The motif of the fading salt is attested in various linguistic and grammatical forms in Matthew 5:13 (Box 1), Mark 9:50 (Box 2), and Luke 14:34–35 (Box 3).

The linguistic similarities and differences point to a common tradition, attested on the one hand in Mark 9:50 and on the other in Matthew 5:13 and Luke 13:34–35 (Fleddermann 1995:166–169). Within the framework of the two-source theory (for the origin, development, and alternative interpretations of the literary relationship between the Synoptic Gospels, see Kloppenborg Verbin 2000), the similarities between Matthew and Luke refer to Q. Both versions, Mark 9:49–50 and Q 14:34–35, differ significantly in how the good salt (only in Mt 5:13a do those addressed become the ‘salt of the earth’) loses its savouriness. In Mark, the verb ἄναλον γένηται is used, whereas in Q the verb μωρανθῇ appears. Only in Mark does the passage conclude with an exhortation to have salt within oneself and to live in peace.

It is frequently assumed that Luke 14:34–35 best preserves the Q-text. The following possible Q-text is discussed below (for the reconstruction of Q, see e.g. Heil 2003: 111–116; for a text reconstruction, see eds. Hoffmann & Heil 2009:98):

³⁴ [Καλὸν] τὸ ἅλας· ἐὰν δὲ τὸ ἅλας μωρανθῇ, ἐν τίνι ἀρτυθήσεται;

³⁵οὔτε εἰς γῆν οὔτε εἰς κοπρίαν [εὔθετόν ἐστιν], ἔξω βάλλουσιν αὐτό.¹

Because of the direct address in Matthew 5:13a [ὑμεῖς ἐστε τὸ ἅλας τῆς γῆς] and the parallel to Mark 9:50a in Luke 14:34a [καλὸν { … } τὸ ἅλας], the question arises whether and how the introduction in Q can be reconstructed. Most scholars follow Luke 14:34a: καλὸν τὸ ἅλας (Fleddermann 1995:167), so that the opening statement begins with a positive evaluation which is contradicted by the following question-and-answer exchange (good ↔ becoming tasteless or foolish [μωρανθῇ]). The direct address in Matthew 5:13, which will be discussed below, is likely to be the work of the Matthean narrator. Regarding the problem of salt losing its flavour and the resulting question of what can be used to season, the texts agree in substance but differ in linguistic detail (Mt 5:13b–c; Lk 14:34b–c). The verb ἀρτυθήσεται (Lk 14:34c) deserves preference over the Matthean ἁλισθήσεται.

That a Q tradition underlies this saying is supported by the agreement between Matthew 5:13d–f and Luke 14:35a–b. In both cases, the consequence for tasteless salt is expressed through similar imagery, with the core statement βληθὲν ἔξω / ἔξω βάλλουσιν αὐτό being consistent. Mark’s statement on peace is absent from both Matthew 5:13 and Luke 14:35 – another point of agreement supporting dependence on Q. In contrast to Mark, both Matthew and Luke end the phrase with a word of destruction, which likely evokes eschatological motifs of judgement. Matthew places the crushing of the salt at the conclusion of the statement, while Luke foregrounds its uselessness.

From these observations, the direct affirmation ‘you are’ in Matthew 5:13a remains striking. How can this Matthean design be explained? As has already been shown, it is unlikely that the Matthean narrator preserves the Q tradition more faithfully here than Luke 14:34a, although Luke may have been influenced by Mark 9:50a. The use of direct address does appear in the Beatitudes of Q, but Luke probably provides stronger evidence for the positioning of the phrase (Heil 2003:111–112). In Q, it likely continues the disciples’ instruction from 14:16–27 (Leonhardt-Balzer 2007:200), so that Q 6:22–23 cannot be considered as an explanation for the direct address in Q.

When the Matthean context is considered, the narrator modifies his Vorlage from Q 6:20–21 into the generalised form μακάριοι οἱ … in Matthew 5:3–10 yet retains the second-person address in 5:11. Matthew 5:14 likewise employs direct address. This latter logion is a special Matthean tradition. Therefore, it seems plausible that Matthew 5:13a has been formulated by the narrator himself, adapting the introduction to conform stylistically with 5:11 and 5:14 (see e.g. Cullmann 1966:195; Fleddermann 1995:167; Gundry 1994:75; Heil 2003:112; ed. Schnackenburg 1971:180).

In comparison with the similarly constructed special tradition in Matthew 5:14, it seems plausible that Matthew drew on a saying about salt from his own Jesus tradition and merged this with the Q text (Strecker 1984:51 refers to ‘in der Urtradition isolierte Herrenworte’ in Mt 5:13–16). Salt played an essential role in everyday Palestinian life, for example in preserving fish around the Sea of Galilee (Zwickel 2005:73–75) and thus offered a vivid and immediately available component for Jesus’s metaphorical proclamation. It is conceivable that a double logion originally existed together with the sayings on salt and light (Mt 5:13a, 14a), which may trace back to the proclamation of the historical Jesus and would similarly be part of the proclamation of the kingdom of God. In that case, it would correspond to the original Beatitudes (Labahn 2024), insofar as these:

What applies to the Beatitudes likewise pertains to the perception of the addressees in Jesus’s words about salt and light.

According to Zimmermann (2022:383), the introductory address constitutes a parable as a short narrative that, ‘reports […] a change in status, and does more than give a description of condition’. In the case of the word ‘salt’, this short narrative takes the form of a pure metaphor, consisting of two otherwise unrelated elements: a group of people is equated with salt. This identification creates a tension that points toward transformation. As addressees of the coming kingdom of God, the addressees become the salt of the earth and the light of the world through Jesus’s performative speech. According to speech act theory, this presupposes that actions are performed through linguistic utterances.

Jesus’s address (the locutionary act) redefines the addressees through a new characterisation (the illocutionary act of labelling) and aims to transform the religious self-perception of the addressees including their deeds (perlocutionary act) (on ‘speech act theory’, cf. J.L. Austin 1962 and Searle 1969; for applications to biblical studies, see e.g. Wagner 1997:7–92; and regarding the Beatitudes, Hellholm 1998:294–298). What emerges here is a form of spiritual transformation, in which God changes human identity through Jesus’s address: (1) as participants in the kingdom of God, they are now the salt of the earth and the light of the world respectively; and (2) as citizens of the emerging kingdom of God, despite their marginal social reality (see also the addressees of the Beatitudes in Q 6:20–21) they have become a new distinct community living and acting according to their renewed identity as part of the dawning kingdom of God. Insofar as the dawning of God’s rule is to be conceived universally, the promise is also to be understood in a generalised and inclusive sense.

The tradition underlying Matthew 5:13a (and 5:14a) with its direct address would then be integrated into the paraenetic framework of the salt saying, which the narrator adopted from Q. It will be demonstrated that Matthew employs the metaphor in such a way that the promise also contains a claim, namely the call to be salt. This connects the encouragement derived from the memory of Jesus and the paraenetic disciple instruction found in Q, which already warned the disciples against becoming tasteless (e.g. Heil 2003:116). Q 14:34 emphasises that eschatological judgement and condemnation await if there is no sufficient, active discipleship according to the standard of Jesus’s words (Labahn 2010:195). The escalation has a performative character motivating the addressees to adopt the appeal (Labahn 2008:277).

After elaborating the use of the salt word in the Jesus memory and its adaptation in the Sermon on the Mount, we now turn to the Old Testament use of salt as a potential background for the salt metaphor in Matthew 5:13. In the Old Testament references, the use of salt has an ambivalent character (for an overview of Old Testament, Jewish, and Greek references on salt, see Davies & Allison 2004:472–473). Salt is mentioned either for its positive effects or for its harmful use – there is no neutral or intermediate usage. This fact needs to be borne in mind when later examining the Matthean salt metaphor in Matthew 5:13.

The negative use of salt primarily concerns its application. In Deuteronomy 29:22, God’s judgement on Sodom and Gomorrah for their lawless behaviour takes the form of burning the land with sulphur and salt. Neither the exact use of the salt nor the process of burning with the sulphur is described in detail, but the effect: the land becomes barren and incapable of sustaining crops. This effectively removes the land from future use and settlement. Likewise, excessive salt in the water of ponds makes the water unfit for irrigation (Ezk 47:11). Salt has the same effect on the city, which, according to the brief note in Judges 9:45, is rendered barren by King Abimelech after his military capture and destruction. The sprinkling of salt on the city is used metaphorically and refers to the fatal effect of an all-encompassing layer of salt. Accordingly, geographical names incorporating the element ‘salt’ (the Salt Sea = Dead Sea: Gn 14:3; Jos 3:16; 12:3; 18:19; the City of Salt: Jos 15:62; Ps 60:2; the Valley of Salt: 1 Chr 18:12; 2 Chr 25:11) are considered barren and uninhabitable, comparable to the desert where, according to Job 39:6, only wild donkeys dwell. The required amount of salt in each case underscores the hyperbolic and metaphorical character of such judgement imagery.

Where salt functions positively, its use concerns daily, moderate quantities. For example, salt serves as seasoning in sacrificial offerings, particularly in grain offerings (Lv 2:13), burnt offerings (Ezk 43:24; Ezr 6:9), as well as in more general terms without specification of offering type (Ezr 7:22). According to Hieke (2014:211), the inclusion of salt applies to all types of grain offerings because the natural seasoning used in human food was not to be withheld from the deity.

Thus, salt is also mentioned in Sir 39:31 (cf. Job 6:6) as a component of essential foodstuffs alongside water, flour, milk, honey, wine, and oil, clothing, as well as fire and iron. This classification of salt may also underlie the so-called ‘salt tax’, which, according to 1 Maccabees 10:29, Demetrius imposed upon the Jews. In such cases, salt is used as a seasoning valued for taste and usefulness in small quantities.

Furthermore, salt could be used for purification. Elijah used salt at water sources (2 Ki 2:20–22), and salt dissolved in water served for bodily cleansing (Ezk 16:4). Eising (2020:912) interprets these uses of salt ‘as a means of health’, as it was also valued in ancient medicine (on salt as remedy, see e.g. Pliny, Nat. 31.80–105).

The so-called covenant of salt is mentioned twice in the Old Testament. If, according to Numbers 18:19, holy offerings are considered a ‘covenant of salt’, the practice of using salt in offerings is likely in the background here. This is also supported by the designation ‘salt of the covenant’ in Leviticus 2:13. The communal character associated with the sacrificial meal ensures the incorporation of the covenant of salt: ‘Das Salz fungiert […] als materiale Realisation und Symbol des Bundesgedankens’ (Hieke 2014:211). The meaning of the covenant of salt in 2 Chronicals 13:5, which merely states that God grants such a covenant of salt, is less clear. Here, the covenant of salt serves as guarantee, representing the immutability and reliability of the divine promises to the Davidic kingship, as evoked from the retrospective view of the Second Temple period.

Japhet (2003:168) describes the covenant expression as a ‘Metapher für eine verpflichtende und unabänderliche Regelung’. She leaves open, however, how the metaphor arises and what precise function salt performs within it. Notably, salt plays no further role in the offering accounts or elsewhere in 1 and 2 Chronicles.

To summarise, the following Table 1 presents a concise overview of the various functions of salt in the Old Testament and early Jewish Septuagint references.

The overview leads to the following conclusion. While the texts on the ‘covenant of salt’ emphasise the various personal dimensions of the covenants – with Aaron and the Aaronic priesthood, and with David and his royal successors – the unifying element is the inviolability of the covenant. Just as salt preserved food from decay, the statement to the ‘covenant of salt’ confirms the permanent and unalterable communal nature of the covenant (cf. Schmidt 2004:81).

In considering the reception of the biblical background within the salt metaphor of Matthew 5:13, the preceding review has shown that none of the passages offers a direct reference to the Old Testament. The motif of ‘salt’ is qualified there in ways that differ significantly from its use in the Sermon on the Mount.

However, there are references to the Old Testament’s use of salt that may have been incorporated in Matthew 5:13. Of particular relevance for the reception of Matthew 5:13a is the use of the covenant of salt as found in Chronicles (according to Beutler 1994:93, who speaks of a ‘dauerhafte[.] Funktion des Jüngerkreises für Israel’). Like the Sermon on the Mount, Chronicles shared the fact that salt is related to people rather than geographical locations or foodstuff. This parallel, however, breaks down in 2 Chronicles 13:5, where it is the kingship itself, and not the kings themselves that is considered as a covenant of salt. In contrast, the metaphor in Matthew 5:13 identifies the ‘you’ group directly with salt. The encouragement assigns a new identity upon the people addressed. Through the speech act, without any action on their part, they become the salt of the earth. The metaphorical character of this transformation will be examined in more detail in the following section. God thus bestows upon them a lasting identity, conceived as participation in the community of God. However, the brief logion lacks any explicit reference to a covenant, and its proximity to the saying about light suggests a use of a basic metaphor of human existence, namely that humans require salt and light to live and survive. A distinction may therefore be drawn between the use of the metaphor in Jesus’s proclaiming and Matthew’s reception of it in the Sermon on the Mount. Even without covenant terminology, Jesus’s address establishes a lasting and unalterable communal character within the kingdom of God as an activity by the one God. Within the context of the Matthean saying about salt, the ‘you’ group thus functions as a community perceived in the world (the earth as ‘place where the community addressed […] lives’; Betz 1995:158) standing out from others because of a distinctive ‘spice’.

In Matthew’s reception, the permanent character of salt, which is crucial for the statement of the covenant of salt, is applied in a paraenetic manner. The impossible, namely the loss of savouriness or transforming into a somewhat new quality, appears as a possibility that must not become reality. Thus, in Matthew 5:13, the concept of salt is not limited to the address but unfolds into a series of sayings built around the key term ‘salt’. A rhetorical question is asked: What happens when salt loses its flavour? With what then, should one add salt? In Matthew, the sequence of key words is intensified through the juxtaposition of ἅλας and ἁλισθήσεται. This creates a break between the unconditional promise, together with newly conferred identity of those addressed, and the potential loss of that identity. Such a bipolar connection between the promise of salvation and the necessary realisation of salvation can already be observed in the Beatitudes. The continuation aligns with the biblically documented and commonly known use of salt as a seasoning.

Another, although less likely, interpretation concerns salt as a cleanser. The aspect of purification aims at demarcating the ‘you’ group from those outside it. Accordingly, the ‘you’ group would represent a group that regards itself as purified, while members of the outside world are considered as impure. A purification process might therefore be required to join the ‘you’ group. Consequently, the ‘you’ group appears as a distinct and ideal entity.

Thus, from these reception aspects, it becomes quite clear that a particular characterisation of the ‘you’ group emerges, as expressed in Matthew’s Sermon on the Mount. However, this reception still reveals little about the ‘you’ group’s identification through the metaphor of ‘salt’ – a matter to which we shall turn to in the next section.

In such a programmatic prologue, the brief salt metaphor in Matthew 5:13a presents itself as a classic ‘pure metaphor’. This observation has received surprisingly little attention in research – perhaps because the promise is so often interpreted together with what follows – as a unit linked to the loss of salt’s taste. Often, only the figurative character of the saying is acknowledged (see e.g. Strecker 1984:51: Bildworte). For example, Hagner (1993:99) suggests ‘to take the metaphor broadly and inclusively’. However, even embedding the metaphor within the context of Matthew 5:13 does not yield significantly greater insight, as the salt, through a wordplay between the noun and the passive verb derived from the same root [ἅλας – ἁλίζω], is ultimately referred back to itself. Furthermore, there is a break between the two statements: the affirmation contains the identification between the human being and salt.

In order to arrive at a closer interpretation, we must firstly focus on the nature of a metaphor and later return to its effect. A pure metaphor consists of two elements that, in themselves, share nothing in common but are nevertheless related to one another – in this case the salt and the ‘you’ group of people. According to the metaphor theory of Lakoff and Johnson (1980), it belongs to the nature of metaphors that both elements mutually exchange their properties. Through this exchange, a transference occurs, resulting in a certain identification between the two elements. With regard to the ‘you’ group, this means that it assumes the characteristics or functions of salt – corresponding to salt’s role as a flavour-enhancing seasoning. The quality of the people addressed as salt also exerts an effect upon the salt itself; this effect is found in the paraenetic continuation, where renunciation of the required action is figuratively portrayed through salt becoming tasteless.

But who are those addressed? The framework of the Sermon on the Mount presents Jesus’s teaching as a public discourse (Mt 5:1); it is therefore directed to the assembled listeners and, in particular, to his disciples. In Matthew 28:20, the Evangelist places these spoken words at the very centre of the disciples’ worldwide missionary work. Those baptised from the world into the community should act according to Jesus’s words, especially the teaching of the Sermon on the Mount. The Beatitudes narrow the circle of those addressed by the Word of Salt (and Light) to those who are invited by God’s blessing and who live accordingly (Mt 5:3–12). As such, they are exposed to persecution and insults (the ‘you’ is already encountered in Mt 5:11–12). Thus, contrary to claims based on rabbinic parallels, this is neither a polemic against Israel (see e.g. ed. Schnackenburg 1971:193) nor a reference to serving rendered for the Land of Israel (Beutler 1994). In the Matthean context, γῆ does not refer to the ‘land’ but rather to the ‘world’, as it is evident from the parallel expression ‘light of the world’ in the immediate context (Mt 5:14) and from the mission command in 28:18–20 (see e.g. Strecker 1984:52). Hence, the community is distinguished by God in the special role ascribed to it within the world (see e.g. Cullmann 1966:196).

The immediate continuation of the metaphor with the negation of salt’s savour, expressed through the aorist passive μωρανθῇ, does not contribute much to clarifying the metaphor’s meaning. The verb μωραίνω is rare in the New Testament; in the sense of ‘to become tasteless’, it occurs only here and in the parallel passage, Luke 14:34. Elsewhere in the New Testament it appears only twice – Romans 1:22 and 1 Corinthians 1:20 – but there in the sense of ‘to become foolish’, the opposite of wisdom (cf. Bauer, Aland & Aland 1988:1075). Davies and Allison (2004:471, 474) and Leonhardt-Balzer (2007:200ff.) view these two meanings as closely related. Hagner (1993:99) traces this double meaning back to the Hebrew root תפל, suggesting that Matthew 5:13 intentionally exploits this link to connect the metaphor with its addressees. However, in our view, the translation within the context of the image of salt (‘to become tasteless’) remains the preferable interpretation.

The intended meaning is that the salt loses its effectiveness (Hagner 1993:98; Leonhardt-Balzer 2007:200; Luz 1985:222). In the ancient encyclopaedia of readers, salt was generally regarded as retaining its potency indefinitely, so that the loss of its effect would represent a hyperbolic intensification of the warning (Heil 2003:113). Regarding the addressed, the implication is that they risk losing their effect. Those addressed in Matthew 5:13a, described by the metaphor as bearers of an exceptional quality – are thus confronted with an impossible possibility: the loss of their own assigned identity. What defines them as ‘salt’ must be preserved by those addressed. Should they cease to be the salt of the earth, they will, as the continuation in Matthew 5:13d–f figuratively describes, be cast upon the ground and thus become like the rest of humankind.

Matthew 5:13d–f adds a word of warning (see e.g. Leonhardt-Balzer 2007:203), declaring that members of the community who do not – or no longer – embody the profile described, will be expelled from the group (βάλλω; a characteristically Matthean term: cf. Mt 3:10; 5:25, 29; 7:19; 18:8–9; see Luz 1985:223). The striking image, ‘They are no longer good for anything, except to be thrown out and trampled under the foot by men’, draws upon Old Testament judgement motifs, particularly from the Book of Isaiah (Is 10:6; 25:10; 63:3, 6; cf. Gnilka 1986:134–135; Grundmann 1981:138). These motifs evoke destruction within eschatological judgement (Mt 3:10; 5:29; 7:19; 18:8).

The statement refers to the conclusion of the Sermon on the Mount (cf. Mt 7:13–29, especially 7:13, 19, 23, 27), where failure to keep Jesus’s words is threatened with eschatological destruction. The measure for remaining ‘salty’ is both Jesus’s encouragement and his demand, which, according to the narrator, are exemplarily unfolded throughout the Sermon on the Mount. This may involve the willingness of those addressed to sacrifice themselves (as suggested in Mt 5:11–12; see e.g. Cullmann 1966:199), but it is not limited to that. In this sense, the word ‘salt’ is not primarily to be applied to the church in its situation of persecution (but see Hare 1993:44: ‘you, who are persecuted for my sake, […] must function as salt’; similarly, Luz 1985:221). Rather, Jesus’s encouragement enables those addressed to become the salt of the earth when they season, that is, shape, the world through their active deeds aligned with his Word.

The use of Old Testament imagery in the immediate context returns us to considering the reception of the Old Testament implications within the salt metaphor. Among the potential implications, the idea of salt as a seasoning carries the greatest weight in the context of the Gospel of Matthew (Luz 1985:222). Salt functions to enhance the flavour of food; it does not introduce a new element to the actual character of the respective dish but rather accentuates what already defines the food being seasoned.

Regarding the characterisation of the community, the question arises: What does the metaphor in Matthew 5:13 depict? As we have seen, the metaphor theory of Lakoff and Johnson (1980), which presupposes the mutual exchange of properties between the two elements, reaches its limits at this point. Building on their approach, Matthew Black’s theory methodological step further by more precisely characterising both components, defining the two elements respectively as ‘tenor’ and ‘vehicle’, or ‘frame’ and ‘focus’, (cf. Black 1962; drawing on Ricœur 1974, 2004; see also Allbritton 1995). Accordingly, the ‘you’ group forms the tenor, representing the subject to be described, while the salt, as vehicle and object, explains the nature of the ‘you’ group. In our view, the strength of the metaphor lies in the fact that it does not separate the aspects of salt as seasoning and seasoning with salt (as claimed by Leonhardt-Balzer 2007:202); rather it combines the essence of discipleship and corresponding action into a unity of soteriological encouragement and ethical demand.

The metaphor thus seeks to establish a specific interpretation of the ‘you’ group, derived from its identification with salt. The metaphor serves to establish a distinctive group identity from Jesus’s words in the Sermon on the Mount – and from the entire Matthean Jesus narrative – which inherently distinguishes between those within and those outside. For the interpretation of the metaphor within the Matthean Sermon on the Mount, this means that the profile of the ‘you’ group is reinforced. Gnilka (1986:133) speaks of ‘Definitionssätzen’ that form the basis of the group’s self-image. The profile of the ‘you’ group is appropriated through Jesus’s words of encouragement. They derive their profile from the proclamation of the kingdom of God and the ongoing involvement of those addressed (salt metaphor). They align themselves according to the standards established by Jesus within the narrative, which serve as a vital bond within the group and among its members. According to Gnilka (1986:137), this includes discipleship, acceptance of the gospel of the kingdom, religious practice, and good works in the sense of social engagement. More generally Grundmann (1981:140) speaks of acts of mercy towards all people. Hagner (1993:97) describes this as an ‘ethical demand of the kingdom, the very essence of discipleship’, and thus largely capturing the narrative integration of the word ‘salt’ within the gospel. Being salt thus entails actively embodying the value system of the Sermon on the Mount and making it a reality in one’s life. The activity of being ‘salt of the earth’, extends to the entire human world (Konradt 2022:316–317; Leonhardt-Balzer 2007:203; see also e.g. Cullmann 1966:200; Strecker 1984:52), particularly in light of the command to love one’s enemies (Mt 5:44). Being salt includes missionary engagement (Frankemölle 1994:216: emphasising identity expressed through deeds as essential missionary activity; similarly to Gundry 1994:75; Luz 1985:225) and active charity toward the world. According to Harrington (1991:83), the image ‘has significance for the world as a whole’.

Thus, to rephrase, the use of the salt metaphor serves to delineate a profile that constructs a distinctive group identity. According to Hagner (1993:101), Matthew 5:13–16 constitutes an ‘affirmation of the unique identity of the disciples’. More specifically, this means that the group’s sense of belonging together, created by references to Jesus and the kingdom of God, leads to a recognisability in the world that distinguishes this group from other social groups. Consequently, the group of Jesus’s followers not only acquires an internal profile but also develops an external border demarcation (see …, e.g. Gnilka 1986:133).

Such a demarcation, however, does not lead to isolation but rather to outward visibility. The profile of the ‘you’ group offers something to the world that can be found only within it (cf. Frankemölle 1994:215; Gnilka 1986:134; Hare 1993:44), simply because it is rooted in the central figure of identity – Jesus. That particular profile is meant to radiate outward, as the following context in Matthew 5:14–16 explains. The group’s profile aims to exert an attractive force upon the outside world – an appeal that invites people to accept the profile and join the group of Jesus’s followers.