Christ's designation for His disciples in the Sermon on the Mount: 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 (Matt 5:13). In the ancient world salt was a preservative, a flavor-enhancer, a covenant-sign (Lev 2:13: the salt of the covenant; Num 18:19; 2 Chr 13:5), and a soil-purifier. Christ's use combines the preservative and covenant senses: His disciples are the agent by which the surrounding culture is kept from decay and the agent through which God's covenant faithfulness reaches the world. Salt that has lost its savour is useless — the warning is sharp: a church or Christian that no longer preserves what God preserves has become functionally trampled.