“the salt of the covenant.” This refers to the ancient salt covenant, which was a binding covenant made by sharing salt in some way, usually eating it. The idea of having the salt covenant as part of the sacrifices and offerings, even the grain offerings, was to ensure the sincerity of the worshiper. God is not a God who wants people to “just go through the motions” of worshiping Him without being sincere. He makes that clear in a number of places in the Bible.
[For more on the salt covenant, see commentary on 2 Chronicles 13:5. For more on God wanting a person’s heart to be right with Him before making sacrifices and offerings, see commentary on Amos 5:22.]
“With all your approach offerings you are to offer salt.” This command here in Leviticus 2:13 made it clear that it was not just the grain offerings that had to be offered with salt, but every offering. The phrase, “all your approach offerings” is literal and means “all,” and there were many different “approach offerings.” The salt emphasized the covenant of the Law that God made with Israel (Exod. 24:3-8) and emphasized the sincerity of the person making the offering, and that was important for every person and every sacrifice and offering. No offering was in and of itself sufficient to cover for sin. The offering had to be done in sincerity of heart, with trust (faith) in God that He would accept the offering and make atonement. David understood that fact well, and expressed it in Psalm 51: “Behold, you desire faithfulness in the inward parts. For you do not delight in sacrifice, or else I would give it. You have no pleasure in a burnt offering. My sacrifice, O God, is a broken spirit. A broken and contrite heart, O God, you will not despise” (Ps. 51:6, 16, 17). Sacrifices without trust in God and obedience to Him were not acceptable to God, a point that the Bible makes clear in many places.
[For more information about the sacrifices of wicked people being of no value, see commentary on Amos 5:22.]