The first portion of your kneading, you shall separate as a dough offering (challah)... In all your generations, give the first of your kneading as an elevated gift to G-d (Numbers 15:20-21)
In its more widely-known usage, the Hebrew word challah refers to the two loaves of bread that form the core of the Shabbat meal. But in its more basic, biblical and halachic meaning, challah is the piece of dough that is traditionally separated and consecrated to G-d every time we bake bread.
The Separation of Challah is one of the 613 mitzvot (divine commandments) that constitute the body and soul of Jewish life. Replete with spiritual meaning, it is one of the three primary mitzvot of the Jewish woman and has a far-reaching effect on the mind and heart of the one who fulfills it, on her household, and on the very character of her home. For more than a hundred generations, Jewish women throughout the world have fulfilled this beautiful and life-transforming mitzvah.