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The Torah prescribes the use of matzo on Pesach as a reminder that during the Exodus the Israelites "baked ... of the dough which they brought forth out of Egypt, unleavened cakes, for it was not leavened, because they were thrust out of Egypt and could not tarry

At the time of the Temple matza flour are also required for the sacrifices, which can not be made from sour dough (Lev.2: 11).