민수기 18:19 할라카: Mishneh Torah, First Fruits and other Gifts to Priests Outside the Sanctuary & Ben Ish Hai

Twenty-four gifts were given to the Priests, and they are all explained in the Torah, and the covenant with Aharon includes all of them. And every Priest that does not recognize these gifts, he is not part of the Priestly tribe, and one must not give him any of these gifts.

The custom is to have a bowl in which to gather the chametz found, with a piece of bread already in it, and to have a knife in order to check the nooks and crannies of the house. There are those who have the custom to place ten morsels of bread in different corners of the house before the search takes place, in order to have something to find and destroy. Here in our city of Baghdad, we place in the aforementioned bowl some salt. The reason is that Satan and his entourage are particularly jealous of the mitzvah of searching for chametz, and the salt repels all these negative forces, in the same way that the kabbalists spoke about the importance of having salt at the table. We also do this for good fortune, that we may merit to perform this mitzvah of searching for chametz for many years to come, since salt lasts for a long time and signifies eternity, as the Torah says: "It is a covenant of salt" (Numbers 18:19)