All the sacred gifts that the Israelites set aside for G-d I give to you, to your sons, and to the daughters that are with you, as a due for all time. It shall be an everlasting covenant of salt before G-d for you and for your offspring as well. (N. 18:19)
What is the word “salt” doing in this verse? After all, what possible change of meaning would there be to the text if it just said “it shall be an everlasting covenant before G-d…”?
The answer is found by understanding that salt is also a requirement with every offering of every kind (not just meat, but also first fruits and … well, everything else a person might bring!):
With every offering of meal shall be salt; you shall not omit from your meal offering the salt of your covenant with God; with all your offerings you must offer salt. (L. 2:13)
Note that the salt connects to a covenant with G-d – both for the offerings and the priests who facilitate those offerings.
What does it mean?
The offer is in the text itself: When they had brought them outside, one said, “Flee for your life! Do not look behind you, nor stop anywhere in the Plain; flee to the hills, lest you be swept away.” …Lot’s wife looked back, and she thereupon turned into a pillar of salt. (G. 19:17)
So the meaning is clear: salt is used to remind us to not look back. Judaism is always about the future and not dwelling on the past. The only way to grow and change is to look forward, to what we can do next.
Lot’s wife is turned into more than just salt: she becomes a netziv, a pillar. In the Torah, a pillar is a memorial, a reminder (Jacob builds them for just this purpose). A netziv physically memorializes a contract. So in the case of Lot’s wife, the pillar of salt becomes a permanent reminder of keeping our focus on our greater purpose. If we look behind us, to our pasts, we risk being distracted from what is in front of our feet.
Every offering of every kind thus is brought with salt, as a reminder to the offeror that the salt, as literally embodied by Lot’s wife, reminds us we are to keep our eyes facing forward.
The priests have a covenant of salt as well, both practically (as salt comes with the offerings, priests receive it as well), and symbolically: the priests are the enablers for the people on their spiritual journey to an ever-closer relationship to G-d.
In this role, priests are thus reminded that as they help the people with offerings, the goal is to focus on building, growing, and looking to the future.