On Christian Doctrine In Four Books

35. But as there are many ways in which things show a likeness to each other, we are not to suppose there is any rule that what a thing signifies by similitude in one place it is to be taken to signify in all other places. For our Lord used leaven both in a bad sense, as when He said, "Beware of the leaven of the Pharisees," I and in a good sense, as when He said, "The kingdom of heaven is like unto leaven, which a woman took and hid in three measures of meal, till the whole was leavened."