Sefer HaChinuch ספר החינוך

The commandment of salting the sacrifice: To offer salt on all of the sacrifices; meaning to say, that he place salt in the meat of the sacrifice and so [too,] in the flour of the meal-offerings, as it is stated (Leviticus 2:13), “upon all your offerings you shall offer salt.”

We have already said in the commandment of the building of the [Temple] (Sefer HaChinukh 95) that it is from the roots of the commandment of the sacrifice to render fit and straighten the soul of the one who offers it. And therefore in order to arouse the soul of the one who offers, he is commanded [to bring as an] offering things that are good, pleasant and beloved to him — and as we wrote above. And the salt in it is also from this root, so that his action be complete, [that] it not lack anything according to the practice of people; since then will his heart be more aroused. As anything without salt is not pleasant to a person — not its flavor and not even its smell. And besides this, there is another matter hinted to with salt, as salt preserves everything and saves from spoiling and rotting. And so [too,] with the procedure of the sacrifice, a man is saved from loss, preserves his soul and will remain in existence forever.

From the laws of the commandment is that which they, may their memory be blessed said (Menachot 20a) that all the sacrifices are salted before they go up to the altar. And you do not have anything that approached the altar without salt, except for the libations, blood and wood. And this thing is a tradition and it does not have a [source in] Scripture. And if he transgressed and sacrificed without salt, the sacrifice is fit and acceptable — except for the meal-offering, [for which] the [lack of] salt invalidates it. As about it is it stated explicitly (Leviticus 2:13), “you shall not omit the salt of your covenant with God from your meal-offering.” And the rest of its details are elucidated in Sifra and in [various] places in Menachot. (See Mishneh Torah, Laws of Things Forbidden on the Altar 5:11.)

And [it] is practiced at the time of the [Temple] by the males of the priesthood. And one who transgresses this and offers a meal-offering or sacrifice without salt has violated this positive commandment; and he further violates a negative commandment, as it is written, “you shall not suppress the salt, etc.”