Verses 15-20 “15Seven days shall ye eat unleavened bread; even the first day ye shall put away leaven out of your houses: for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.
16And in the first day there shall be an holy convocation, and in the seventh day there shall be an holy convocation to you; no manner of work shall be done in them, save that which every man must eat, that only may be done of you.
17And ye shall observe the feast of unleavened bread; for in this selfsame day have I brought your armies out of the land of Egypt: therefore shall ye observe this day in your generations by an ordinance for ever.
18In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one and twentieth day of the month at even.
19Seven 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.
20Ye shall eat nothing leavened; in all your habitations shall ye eat unleavened bread.”
Leaven is a type of sin in the Bible. It is never a symbol of the gospel or of anything good. Leaven is a type of sin because it is pervasive, it is a form of spoilage, and it grows. The Hebrews putting away all leaven, eating meals without leaven, and searching their houses to get all the leaven out teaches us that God is pleased when we put away sin from our lives.