And every oblation of thy meat offering shalt thou season with salt; neither shalt thou suffer the salt of the covenant of thy God to be lacking from thy meat offering: with all thine offerings thou shalt offer salt. (2:13)

--Numbers--

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. (18:19)

--2 Chronicles--

Ought ye not to know that the Lord God of Israel gave the kingdom over Israel to David for ever, [even] to him and to his sons by a covenant of salt? (13:5)