Matthew 5:13

τὸ ἅλας τῆς γῆς. Salt (1) preserves from corruption; (2) gives taste to all that is insipid; (3) is essential to all organised life. So the Apostles alone can save the world from corruption; the gospel alone can give zest and meaning to society; it is essential to the life of the world.

ἅλας. Late as a literary word for ἅλς, but it occurs in the adage ἅλασιν ὕει. In Mark 9:49 both forms are used according to the best reading, τὸ ἅλας and accus. ἅλα, dat. ἁλὶ from ἅλς. In Colossians 4:6, the dat. ἅλατι of the neuter form is used. Attic prose has the plural only.

ἐὰν μωρανθῇ. The causal force of μωραίνω is Hellenistic; in the classical period the meaning is ‘to be foolish.’ For the use of the word in a literal sense cp. Romans 1:22, φάσκοντες εἶναι σοφοὶ ἐμωράνθησαν. And for the interchange of meaning between folly and insipidity cp. sapere, sapientia, insipidus; sal, sales, ‘salt’, then ‘wit’ (so in late Greek ἅλες); insulsus, ‘unsalted,’ then ‘stupid’.

ἐν τίνι. ἐν is here clearly instrumental, see ch. Matthew 3:11.

καταπατεῖσθαι ὑπὸ τῶν�. Thomson, Land and Book, 382, describes ‘the sweeping out of the spoiled salt and casting it into the streets’ as ‘actions familiar to all men.’