The prohibited foods render impure those who eat them, while abstaining from them causes a person to be sanctified. Every minute action of a person carries significant consequences.

The Sages taught: The verse states: “And you shall not be rendered impure by them, and become impure through them” (Leviticus 11:43). [The repetition of the word impure means that] if a person renders himself a little impure, he is rendered extremely impure; if a person renders himself impure from below [at his own initiative], he is rendered impure from above; if a person renders himself impure in this world, he is rendered impure in the World to Come. The Sages taught: The verse states: “You shall sanctify yourselves and be sanctified” (11:44). [The repetition of a term of sanctity means that] if a person sanctifies himself a little, he is sanctified a lot; if a person sanctifies himself from below, he is sanctified from above; if a person sanctifies himself in this world, he is sanctified in the World to Come. (Yoma 39a)