Bible Verses About Salt: Ratifying covenants

All the contributions of holy things which the people of Isra'el offer to ADONAI I have given to you, your sons and your daughters with you; this is a perpetual law, an eternal covenant of salt before ADONAI for you and your descendants with you."

Don't you know that ADONAI, the God of Isra'el, gave rulership over Isra'el to David forever, to him and his descendants, by a covenant of salt [which is unbreakable]?