1.
COVENANT OF SALT

From SEFARIA - https://www.sefaria.org/

A.
Vayikra - Leviticus 2:13:
You shall season your every offering of meal with salt; you shall not omit from your meal offering the salt of your covenant with God; with all your offerings you must offer salt.
B1.
Ibn Ezra on Vayikra - Leviticus 2:13:
THE COVENANT OF THY GOD.
God caused you to enter the covenant and made you swear that you would not offer anything which is unsalted and inedible, for that is an insult [to God].
B2.
Ibn Ezra on Bamidbar - Numbers 18:19:
THE COVENANT OF SALT.
A “cut covenant.” [The Biblical term for making a covenant is, to cut a covenant. Hence I.E.’s note that a salt covenant is a variant of a cut covenant.] The word melach (salt) is related to the word melechah (salt) [In that both words have the meaning of cut.]
In A fruitful land turned into salt (Tehillim - Psalms 107:34). A salted place is said to be cut off, for nothing grows there.
C.
Ramban on Vayikra - Leviticus 2:13:
NEITHER SHALT THOU SUFFER THE SALT OF THE COVENANT OF THY G-D TO BE LACKING FROM THY MEAL-OFFERING.
“For a covenant was established with salt as far back as the six days of Creation, for the lower waters [i.e., those of the oceans] were promised that they would be offered upon the altar in the form of salt, and [also as water] at the libation of water, on the Festival of Tabernacles.” This is Rashi’s language, and it is a homiletic exposition of the Sages.
Rabbi Abraham ibn Ezra interpreted it in line with the plain meaning of Scripture as follows: “I have brought you into a covenant and made you swear that you would not offer a saltless offering, nor shall it [i.e., a saltless offering] be eaten, because it is a mark of contempt.”
Now since salt is the covenant of the offerings, Scripture made this accord the pattern for all such agreements, saying of the gifts given to priests and the dynasty of David that they are [an everlasting] covenant of salt, meaning that they are as everlasting as the covenant of salt of the offerings. There, however, Rabbi Abraham ibn Ezra explained: “A covenant of salt — a covenant decreed, it being of the root, a fruitful land into a salt waste, since a salt waste is as if it has been decreed [upon it that nothing should grow therein].” But there is no sense to his words. Now it seems to me that since Scripture here states, the covenant of thy G-d, and does not say “the covenant of the Eternal,” which would have been in consonance with the language of the section and the way all the offerings are mentioned [throughout Scripture], or did not say, “the covenant of the Eternal thy G-d” — that the reason for this is because salt is derived from water, and it is through the power of the sun which shines upon it that it becomes salt. Now the nature of water is that it soaks into the earth and makes it bring forth and bud; but after it becomes salt it destroys every place and burns it, that it is not sown, nor beareth. Since a covenant is inclusive of all attributes, water and fire come into it, and unto her shall come the former dominion — the Kingdom of G-d, just like salt which seasons all foods and helps to preserve them, but destroys them when they are over-saturated with it. Thus salt is like the covenant. It is for this reason that Scripture states, Ought ye not to know that the Eternal, the G-d of Israel, gave the kingdom over Israel to David forever, even to him and to his sons by a covenant of salt forever? For this too is the attribute of David. Therefore He says in connection with the offerings, it is an everlasting covenant of salt, for the covenant is “the salt of the world,” and by virtue of it [the world] exists or may be destroyed. I have already taught you to understand from our words in other places the meaning of these three words, brith olam hi (it is a perpetual covenant).