THE LEAVEN 

1 Corinthians 5:7-8 Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our Passover is sacrificed for us: (8) Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth. 

PASSOVER/FEAST OF UNLEAVENED BREAD ORIGIN/HISTORY

The Passover and the Feast of Unleavened Bread is an ordered feast that commemorates the great deliverance of the children of Israel from the bondage of Pharaoh and the Egyptians by the Most High sending the destroyer to smite the firstborn of Egypt.

Exodus 12:21-24 Then Moses called for all the elders of Israel, and said unto them, Draw out and take you a lamb according to your families, and kill the Passover. (22)  And ye shall take a bunch of hyssop, and dip it in the blood that is in the bason, and strike the lintel and the two side posts with the blood that is in the bason; and none of you shall go out at the door of his house until the morning. (23)  For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you. (24) And ye shall observe this thing for an ordinance to thee and to thy sons for ever. 

Exodus 12:29-31 And it came to pass, that at midnight the LORD smote all the firstborn in the land of Egypt, from the firstborn of Pharaoh that sat on his throne unto the firstborn of the captive that was in the dungeon; and all the firstborn of cattle. (30) And Pharaoh rose up in the night, he, and all his servants, and all the Egyptians; and there was a great cry in Egypt; for there was not a house where there was not one dead. (31)  And he called for Moses and Aaron by night, and said, Rise up, and get you forth from among my people, both ye and the children of Israel; and go, serve the LORD, as ye have said. 

ORDINANCES OF THE FEAST

Leviticus 23:2 Speak unto the children of Israel, and say unto them, Concerning the feasts of the LORD, which ye shall proclaim to be holy convocations, even these are my feasts.

Leviticus 23:4-8 These are the feasts of the LORD, even holy convocations, which ye shall proclaim in their seasons. (5) In the fourteenth day of the first month at even is the LORD’S Passover. (6) And on the fifteenth day of the same month is the feast of unleavened bread unto the LORD: seven days ye must eat unleavened bread. (7) In the first day ye shall have an holy convocation: ye shall do no servile work therein. (8) But ye shall offer an offering made by fire unto the LORD seven days: in the seventh day is an holy convocation: ye shall do no servile work therein.

OBSERVATION OF PASSOVER/FEAST OF UNLEAVENED BREAD IN CHRIST

When you examine the scriptures, you find the lamb that was killed as the Passover was a sacrifice.

Exodus 12:26-27 And it shall come to pass, when your children shall say unto you, What mean ye by this service? (27) That ye shall say, It is the sacrifice of the LORD’S Passover, who passed over the houses of the children of Israel in Egypt, when he smote the Egyptians, and delivered our houses. And the people bowed the head and worshipped.

According to the new covenant Christ is our atonement and has reconciled all of our sacrifices by dying and shedding his blood as the last and perfect sacrifice.

Romans 5:10-11 For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life. (11) And not only so, but we also joy in God through our Lord Jesus Christ, by whom we have now received the atonement. 

1 Peter 1:18-19 Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers; (19) But with the precious blood of Christ, as of a lamb without blemish and without spot. 

More specifically, concerning the lamb that was killed as the Passover, Christ in life and also in the way he died was symbolic of the sacrifice of the Passover. A quick examination of the following scriptures supports Christ symbolism as the Passover Lamb.

John 1:29 The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world. 

1 Peter 1:19 But with the precious blood of Christ, as of a lamb without blemish and without spot. 

Luke 23:50 And, behold, there was a man named Joseph, a counsellor; and he was a good man, and a just: 

Luke 23:52 This man went unto Pilate, and begged the body of Jesus. (53) And he took it down, and wrapped it in linen, and laid it in a sepulchre that was hewn in stone, wherein never man before was laid. (54) And that day was the preparation, and the sabbath drew on. 

Exodus 12:5-6 Your lamb shall be without blemish, a male of the first year: ye shall take it out from the sheep, or from the goats: (6) And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening. 

1 Corinthians 5:7 Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our Passover is sacrificed for us: 

Our forefathers observed this day by removing all leavened bread out of their dwelling place. In these times, we must observe this ordinance according to the teachings of Jesus Christ by purging our minds of perversions, and wickedness and keep the feast in soberness, sincerity, and truth.

Hebrews 9:13 For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh: (14)  How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God? 

1 Corinthians 5:8 Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.