In ancient times salt could not be destroyed by fire or any other means. By adding salt to the offering, the worshipper was reminded of their eternal relationship with the Lord. This meant that the Lord would never forsake his people. At the same time, the worshipper was reminded of their duty to uphold the law.
13 Tu mettras du sel sur toutes tes offrandes; tu ne laisseras point ton offrande manquer de sel, signe de l'alliance de ton Dieu; sur toutes tes offrandes tu mettras du sel.