In the war with Midyan, the Israelites seized considerable spoils, among them utensils used with food. The Torah provides methods of rendering utensils kosher, based on their previous uses. According to what is written in the Torah portion, the Sages established fundamental principles concerning how to render utensils kosher.

In the case of one who acquires utensils from a gentile, if he acquires those utensils whose manner is to immerse them in a ritual bath, he must immerse them accordingly. If he acquires those whose manner is to purge them, he must purge them accordingly. If he acquires those whose manner is to heat in the fire until white-hot, he must heat them in the fire until white-hot. If he acquires a spit or a grill, he must heat them in the fire until white-hot. If he acquires a knife, he rubs it and it is purified. The Sages taught: And all these utensils acquired from a gentile require immersion in forty (Avoda Zara 75b)