Bible verses about Leaven (yeast)
(From Nave's Topical Bible)

LEAVEN (YEAST) -For bread Exodus 12:34, 39; Hosea 7:4; Matthew 13:33 -Leavened bread used .With a peace-offering Leviticus 7:13; Amos 4:5 .With a wave-offering Leviticus 23:15-17 -Leavened bread forbidden .With meat offerings Leviticus 2:11; 6:17; 10:12; Exodus 23:18; 34:25 .At the Passover meal 13:3, Exodus 12:19, 20; 4, 7; 23:18 .With blood Exodus 23:18; 34:25 -A symbol for sin I Corinthians 5:6-8 -FIGURATIVE .Of the hypocrisy of the Pharisees Matthew 16:6-12; Mark 8:15; Luke 12:1 .Of other evils I Corinthians 5:6-8; Galatians 5:9 .Parable of Matthew 13:33; Luke 13:21