John_Chrysostom“Ye are the salt of the earth: but if the salt have lost his savour, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men” (Matthew 5:13).

Now then, after giving the disciples due exhortation [i.e. in the Beatitudes], Jesus refreshes them again with praises.

The injunctions being high, and far surpassing those in the Old Testament; lest they should be disturbed and confounded, He does not want them to say, “How shall we be able to achieve these things?”

Hear, then,  what He says: “Ye are the salt of the earth.”

[…] For “not for your own life apart,” says He, “but for the whole world, shall your account be.

“For not to two cities, nor to ten or twenty, nor to a single nation am I sending you, as I sent the prophets; but to earth, and sea, and the whole world; and that in evil case.”

For by saying, “Ye are the salt of the earth,” He signified all human nature to have “lost its savor,”and to be decayed by our sins.

For which cause, you see, He requires of them such virtues, as are most necessary and useful for the superintendence of the common sort.

For first, the meek, and yielding, and merciful, and righteous, shuts not up his good deeds unto himself only, but also provides that these good fountains should run over for the benefit of others.

And he again who is pure in heart, and a peacemaker, and is persecuted for the truth’s sake; he again orders his way of life for the common good.

“Think not then,” He says, “that ye are drawn on to ordinary conflicts, or that for some small matters you are to give account.”

“Ye are the salt of the earth.” What then? Did they restore the decayed? By no means; for neither is it possible to do any good to that which is already spoilt, by sprinkling it with salt.

This therefore they did not. But rather, what things had been before restored, and committed to their charge, and freed from that ill savor, these they then salted, maintaining and preserving them in that freshness,which they had received of the Lord.

For that men should be set free from the rottenness of their sins was the good work of Christ; but their not returning to it again any more was the object of these men’s diligence and travail.

[…]  “But if the salt have lost its savor, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men.”

[…] He tells them, “unless ye are prepared to combat with all this, ye have been chosen in vain.” For it is not evil report that ye should fear, but lest ye should prove partners in dissimulation. For then, “Ye will lose your savor, and be trodden under foot.”

John Chrysostom (c.347-407): Homilies on the Gospel According to St Matthew, 15, 10.