1 Corinthians 5:8
Therefore let us keep the feast, not with the old bread, leavened with malice and wickedness, but with the unleavened bread of sincerity and of truth.

Exodus 12:15
For seven days you must eat unleavened bread. On the first day you are to remove the yeast from your houses. Whoever eats anything leavened from the first day through the seventh must be cut off from Israel.

Exodus 12:19
For seven days there must be no yeast found in your houses. If anyone eats something leavened, that person, whether a foreigner or native of the land, must be cut off from the congregation of Israel.