Pesach, the Passover Seder, tells the story of deliverance, freedom, and redemption. Death passed over those who exercised active faith in YHWH by putting lamb's blood on the doorposts. The Second Death (Hell, Rev. 2:11, Rev. 20:14) passes over the Christian, since the Christian is marked by the blood of Christ.
Tradition teaches us that we must all consider ourselves as slaves in Egypt (Rom. 6:6, Rom. 6:16-22) that we must all consider ourselves to have walked in darkness (Rom. 3:23), so that we might celebrate the deliverance in the Exodus as our own deliverance (Rom. 6:7, Rom. 6:18, Rom. 6:20, Rom. 6:22, Rom. 8:2, Heb. 9:15, Rev. 1:6).
At the death of Jesus, the great veil which guarded the Holy Place within the Temple was supernaturally ripped from top to bottom (Matthew 27:51). As is made clear in the book of Hebrews (Hebrews 9, Hebrews 10), access to God the Father in heaven is now open to all who call upon Jesus Christ - both Jew and Gentile.
Animal sacrifices, since then, were no longer required as part of the true worship. And the Temple being destroyed in AD 70 assured that they were no longer possible. Jesus had forecast this to the Samaritan woman: "The hour comes when you shall neither in this mountain [in Samaria] nor yet at Jerusalem [in the Temple] worship the Father..." (John 4:21). The purpose of all the animal sacrifices was fulfilled in Christ (Hebrews 10).
No more is there a "blood sacrifice," for Jesus Christ, in His suffering and death, perfectly fulfilled the foreshadowing Passover symbolism. By His blood - shed once, for all - He covers and forgives our sin, delivering us from eternal death, and the indwelling Holy Spirit releases us from the slavery of our human nature.
Then, by His victorious, overcoming resurrection from the dead, Jesus was credentialed as the Son of God, making possible our eternal redemption.
On the 14th day of the month of Nisan in the Hebrew calendar, the Passover lamb was sacrificed. The 15th is the first day of the seven-day long Unleavened Bread Festival (Leviticus 23) in spring. On that night, death passed by the children of Israel, protected in their blood-bedecked homes. In that night they began to leave Egypt after decades of enslavement - for freedom.
Probably the most significant observance related to Pesach involves the removal of chametz (sounds like "hum it's" with that Scottish "ch") from Jewish homes. This commemorates the fact that the Jews leaving Egypt were in a hurry, and did not have time to let their bread rise.
The process of cleaning the home of all chametz (leaven) in preparation for Pesach is an enormous task. To do it right, you must prepare for several weeks and spend several days scrubbing everything down, going over the edges of your stove and refrigerator with a toothpick and a Q-Tip, covering all surfaces that come in contact with food with foil or shelf-liner, etc., etc., etc. After the cleaning is completed, the morning before the Seder, a formal search of the house for chametz is undertaken, and any remaining chametz is burned.
Leaven (yeast) is a necessary element in baking and wine-making. However, it was viewed somewhat ambiguously because it also has the power to decay and destroy. Even Jesus used it as both a positive and negative metaphor. In Jewish tradition, it came to have more of a negative connotation as a religious symbol, signifying the potential for corruption and sin.
Therefore, the removal of leaven carries with it deeper significance in Passover than simply its connection with the exodus. Its removal, and the symbolic removal at the beginning of the Seder, signifies the attitude of penitence, the willingness to remove any corrupting influence in one’s life and submit to God in obedience. As the Israelites prepared for the exodus by obeying the commands of God through Moses, so in removing the chametz (leaven, or yeast), we symbolize our willingness to obey God in preparation for celebrating the deliverance he has already brought to His people. We should search for any hidden sins in our hearts, for it is sin that keeps us from intimate fellowship with God.
This shows how serious God is about sin. Even the smallest sin can keep a person out of Heaven. Since every person has sinned, that's why only Jesus can save us from Hell. The removal of leaven also shows that, when a person surrenders their life to Christ and becomes regenerated by the power of the Holy Spirit, the holiness of Christ is transferred to them, and they are considered positionally sinless in the eyes of God. On another level, the removal of leaven also symbolizes the sanctification process of the Christian. As the Christian gets to know Christ Jesus better and better, he or she should be becoming more and more Christlike, and obeying God more and more.
The Israelites were not merely to remove all leavening and leavened foods from their property. That would have only symbolized putting away sin. They were commanded to eat unleavened bread during the Feast of Unleavened Bread. This act of eating unleavened bread symbolizes the opposite of sin, which is active obedience to God.
Jesus warns us in Luke 12:1 about leaven: "Beware of the leaven of the Pharisees, which is hypocrisy."
Throughout Matthew 23, Jesus lists a multitude of Pharisaical sins that could be grouped as legalistic externalism.
In Matthew 16:6, Jesus warns of the leaven of the Sadducees. The Sadducees' sins are not listed, but elsewhere we find they at least denied the supernatural and the resurrection of the dead (Acts 23:8).
Jesus also warns of the leaven of Herod (Mark 8:15). Herod was involved in a great deal of lying in his political wheeling and dealing, abusing the power of his office, adultery, and general all-around worldliness.
Paul commands in 1 Corinthians 5:7-8:
"Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us. Therefore let us keep the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth."
Christians have been sanctified (made holy and set apart for God), regenerated ('born again;' made into new creatures, 2 Cor. 5:17, Gal. 6:15), justified (declared innocent, since, legally speaking, Jesus provided our bail by being surety for us and paying our debt with His blood). Christians are also being sanctified (purified) by God's Word, through suffering, by the washing of Jesus' blood, and by being constantly filled with the Holy Spirit. We are to demonstrate the reality of our salvation in our daily lives. What has been done in us must be worked outward, so that the holiness which we have been given positionally becomes more and more evident in our lives.
some of the above information is from:
The Christian Meaning of the Lord's Supper and Passover