It has been common throughout history for people to confirm their agreements with each other by eating and drinking together, at which times salt is used. As salt was added to foods, not only for spice but also to preserve them from decay, it became a symbol of incorruptibility and permanence. A "covenant of salt" signified an everlasting covenant. In the Bible, salt also came to symbolize purity, perfection, wisdom, hospitality, durability, and fidelity.
Like frankincense and honey, salt and leaven also produce contrasting reactions when used. Salt preserves from corruption, while leaven corrupts and deteriorates what it is inserted into. Unlike frankincense and honey, the Scriptures contain a great deal about these two in their application to the meal offering.
» II Chronicles 13:5: Should you not know that the LORD God of Israel gave the dominion over Israel to David forever, to him and his sons, by a covenant of salt?
» Psalm 89:34-37: My covenant will I not break, nor alter the word that is gone out of My lips. Once I have sworn by My holiness; I will not lie to David: His seed shall endure forever, and his throne as the sun before Me, it shall be established forever like the moon, even like the faithful witness in the sky. Selah.
Here, a covenant of salt suggests an agreement of enduring qualities, even forever. Thus a covenant of salt is one that is very strong, though it may not always be everlasting. Salt is understood to be the preservative, suggesting endurance. When God makes use of this metaphor, He is urging us to be faithful despite how circumstances appear on the surface because His Word is absolutely sure. Like Himself, His Word endures forever.
Salt was required in every sacrifice burned on the altar. Besides its preserving factor, it also has a purifying affect on what it comes in contact with. Ezekiel 16:4 records that newborn babies were rubbed with salt. In addition, Elisha treated a bad water supply in Jericho with salt. Besides purifying, then, it also signifies a new beginning.
John W. Ritenbaugh
The Offerings of Leviticus (Part Three): The Meal Offering