ANSWER: A covenant is simply an agreement or vow between two or parties. The word 'salt' occurs thirty-one times in the King James Old Testament but only ten times in the New Testament. The phrase "covenant of salt" or variation thereof occurs only three times in the entire Bible (Leviticus 2:13, Numbers 18:19, 2Chronicles 13:5).
It is helpful to understand a little background concerning salt before delving into its Biblical relationship with a covenant. Refrigeration as a means of preserving large quantities of food did not begin to grow until the latter part of the 19th century. Before this time, one of the primary ways of preserving food (especially meat) from putrefaction and decay was with salt.
The ability of salt to preserve food from decaying, and thus allow it to be stored and eaten at a future date, was well known to the ancients. The mineral itself was so rare, and such a valuable commodity, that it was sometimes referred to as "white gold." Some of the oldest trade routes in the world were used for the transportation of this percious mineral.
The first reference linking this mineral to a covenant is in book of Leviticus. It states, ". . . And you shall not allow the salt of the covenant of your God to be lacking from your grain offering . . ." (Leviticus 2:13, HBFV throughout). The mineral was an essential ingredient in offerings made to God. Its preservation ability made it an excellent symbol to represent the perpetual agreement between Him and his people.
The second reference in Scripture to this type of covenant is in Numbers 18, where God promises to provide for the needs of his priests. It states, "All the heave offerings of the holy things, which the children of Israel offer to the LORD, I have given you and your sons and your daughters with you by a statute forever. It is a covenant of salt forever before the LORD to you and to your seed with you" (Numbers 18:19).
The last, and perhaps most well known, covenant of this type is found in 2Chronicles 13. King Abijah of Judah used the term to refer to the royal Davidic dynasty's right to rule over Israel in place of the (rebel) King Jeroboam of Israel. He stated, "Should you not know that the LORD God of Israel gave the kingdom over Israel to David forever, to him and to his sons by a covenant of salt?" (2Chronicles 13:5).
Taken together, a 'covenant of salt' is an agreement or contract between parties that endures regardless of the circumstances. It was an ancient symbol of unbreakable friendships and enduring alliances. Such agreements are solid, unbreakable and everlasting.