This is a common metaphor for what we take in and subsist upon, spiritually; whether sanctifying truth, or the world’s carnality and vanities.

There are two purposes for “salt”. Both of which, are expressed in scripture; 1) “Salt” as a natural preservative, and 2) “Salt” as a means of seasoning food to make it palatable.

God told Aaron that the offerings of the holy gifts He was giving to Aaron and his sons as an “everlasting covenant of salt”. In this case, salt is invoked for its quality as a preservative, and therefore constitutes an allusion to things “eternal”. This idea is also expressed in a statement by one of the kings of Judah:

Do you not know that the Lord God of Israel gave the rule over Israel
forever to David & his sons by a covenant of salt?
II Chron. 13:5

As we proceed further into Israel’s history, the meaning of the covenant begins to take on added dimension. We know that David stands as a type for Jesus Christ. His sons stand for the sanctified of Christ; a work of grace. Therefore “salt” now takes on a dual meaning.

Do not be carried away by varied & strange teachings;
For it is good for the heart to be strengthened by grace,
not by foods, through which those who were thus occupied were not benefited.
For we have an alter, from which those who serve the tabernacle have no right to eat.
Heb. 13:9-10

What is this “alter” to which the writer refers? Earlier, the writer encourages us to; “come boldly before the throne of grace, that we may receive mercy, & find grace to help in time of need.” This is a recourse that those that are of the Law do not have access to. Is there any other recourse to but the “throne of God” through which to acquire the “grace of God”? How sad then, that these that are “of the Law” and work so hard in the furtherance of the Law, cannot even please the God they strive to serve! For God has told them that:

Every grain offering of yours, . . . . you shall season with salt,
so that the salt of the covenant of your God shall not be lacking from your grain offering; with all your offerings you shall offer salt.
Lev. 2:13

But where is that “salt” to be found? In a place that “those of the Law” have no access to!

Why would God require that all of our offerings to Him include a salting of “grace”? Without “grace” we are simply offering God our own works; things which are despised, cannot save, and in fact, hinder and obstruct that thing which can save; ie. “faith in Jesus Christ”. What we offer God might be proper and correct in all respects as is concerned with men, but if it is not of “grace” then it is dead unto God.

Given that everything we do, say, or even think constitutes an offering unto God, what should be included in all of our doings, sayings, and thoughts?

Let your speech always be with grace, seasoned, as it were, with salt.
Col. 4:6