The 133rd mitzvah is that we are commanded to separate challah from each dough and to give it to a kohen.

The source of this commandment is G‑d's statement,1 "You must separate the first portion of your kneading as challah [a dough offering]."

The details of this mitzvah are explained in tractates Challah and Orlah. It is a Biblical commandment only in Eretz Yisroel.2