LEAVEN

(Lat. levare, to raise.) A piece of sour dough used to ferment and render light a much greater quantity of dough or paste. By the law of Moses leaven was strictly forbidden during the Pa over; and the Jews, taught to regard it from the vigil of the feast as unclean, with religious scrupulosity purified their houses from the contaminating influence. In its figurative sense. leaven is applied to any thing that powerfully but gradually deteriorates the qualities of the mind or heart: in contradistinction to the expre ion unleavened, which implies the qualities of sincerity and truth. [s. 662]