Ambrose of Milan — as excerpted in the Catena Aurea on Luke 13:18-21

“Many think Christ is the leaven, for leaven which is made from meal, excels its kind in strength, not in appearance. So also Christ (according to the Fathers) shone forth above others equal in body, but unapproachable in excellence. The Holy Church therefore represents the type of the woman, of whom it is added, Which a woman, took and hid in three measures (sata) of meal, till the whole was leavened.”