3,645. When the Obligation of Challah Takes Effect

Hilchos Bikkurim 8:4

The obligation to take challah from dough kicks in when wheat flour is rolled and all the flour is mixed with water, or when barley flour is formed into one mass. A person may snack from a dough until these things are done. The rules of wheat flour also apply to spelt flour, while the rules of barley flour also apply to oat flour and rye flour.

Hilchos Bikkurim 8:5

Once the wheat flour is rolled or barley flour is formed into a mass, whoever eats from it before challah is taken is liable to the penalty of “death at the hands of Heaven” because it’s tevel (untithed produce). Therefore, if it’s a dough that has a Biblical obligation to take challah from, one who eats it is liable to the penalty of lashes, the same as anyone who eats tevel. If the dough has a Rabbinic obligation in challah, one who eats from it is liable to stripes for acting rebelliously.