All the heave offerings of the holy things, which the children of Israel offer unto the Lord, have I given thee, and thy sons and thy daughters with thee, by a statute for ever: it is a covenant of salt for ever before the Lord unto thee and to thy seed with thee. (Numbers 18:19)
An indissoluble covenant, one that never decays, a bond of sacred friendship. Salt, itself a preservative, is an appropriate symbol of that which is incorruptible. It is an emblem of a binding alliance, as when two men would eat bread and salt together. Salt was always added to the sacrifices made to the Lord (Lev. 2:13; Mark 9:49).