'Yeast' in the Bible

"'Seven days you shall eat unleavened bread; even the first day you shall put away yeast out of your houses, for whoever eats leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.

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.

Unleavened bread shall be eaten throughout the seven days; and no leavened bread shall be seen with you, neither shall there be yeast seen with you, in all your borders.