Leaven
'Leaven' signifies evil and falsity which should not be mixed with good and true things.
(Reference: Arcana Coelestia 2342; Exodus 12:15, 12:18-20; Leviticus 2:11)
Exodus 12:18-20
18
In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, until the twenty first day of the month at evening.
19
Seven days shall there be no yeast found in your houses, for whoever eats that which is leavened, that soul shall be cut off from the congregation of Israel, whether he be a foreigner, or one who is born in the land.
20
You shall eat nothing leavened. In all your habitations you shall eat unleavened bread.'"
