Translation:Shulchan Aruch/Yoreh Deah/322
Seif 1: It is a positive commandment to set aside terumah [priestly tithe on produce] from the dough and to give it to a kohen, as it says, “the first yield of your dough, a loaf as a gift,” but this first yield does not have a [fixed] measure from the Torah – even one who separates the amount of a barley-grain has exempted the dough. One who makes all his dough into challah, he has done nothing—rather, he must leave some amount of it. But according to the words of the Sages, one should separate 1:24 from the dough, and a baker who bakes to sell in the shuk should separate 1:48. Also, if the dough becomes impure by mistake or by compulsion, even the householder separates 1:48.
Seif 2: One is not obligated [to take] challah from the Torah except in Israel, as it says, “and you eat of the bread of the land,” and at the time when all Israel was there, as it says, “in your coming,” – the coming of all of you, and not some of you. Therefore [taking] challah at this time and even in the days of Ezra in Israel was only from their words [of the Sages].
Seif 3: We separate challah outside of Israel according to the words of the scribes in order that the law of challah will not be forgotten in Israel.