Sa. It is customary to knead matzah for the mitzvah on the eve of Passover after six hours, which is the time for the offering of the Passover sacrifice. And on the 14th [of Nisan] when it falls on a Sabbath, knead it on the eve of the Sabbath after six hours. And one should say at the time of kneading: Any crumbs that fall during kneading and preparation, and likewise dough stuck to utensils, I nullify them so that they will be annulled before they ferment.