Unleavened bread shall be eaten seven days; and there shall no leavened bread be seen with thee, neither shall there be leaven seen with thee in all thy quarters.
Exodus 12:19
Seven days shall there be no leaven found in your houses: for whosoever eateth that which is leavened, even that soul shall be cut off from the congregation of Israel, whether he be a stranger, or born in the land.
Matthew 16:6
Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the Sadducees.