The Greek word translated in 1Corinthians 10:16 as "communion" is koinonia. The word means to participate or share something with others. The New American Standard Bible translates 1Corinthians 10:16 as the following.
"Is not the cup of blessing which we bless a sharing in the blood of Christ? Is not the bread which we break a sharing in the body of Christ?" (1Corinthians 10:16, NASB)
When a repentant believer partakes of baptism, he shares in the death of Christ. His "old man" or former way of living dies. When they partake of the symbols instituted by Jesus, they again participate or share in his death. For the Christian, the meaning of Passover is that it is a reminder of the commitment made to God at baptism.
At sunset which began Nisan (Abib) 15, twenty-four hours after the children of Israel observed the Passover, they left Egypt and Egyptian slavery (Numbers 33:1, 3-4, Deuteronomy 16:1).
The Night to be much Observed
God commanded Israel to celebrate, each year, their departure from Egypt. This celebration was to occur on the anniversary of their exodus, right after sunset that began Nisan 15.
"And it came to pass at the end of the four hundred and thirty years — on that very same day — it came to pass that all the armies of the Lord went out from the land of Egypt. IT IS A NIGHT OF SOLEMN OBSERVANCE TO THE LORD for bringing them out of the land of Egypt. This is that night of the Lord, A SOLEMN OBSERVANCE FOR ALL THE CHILDREN OF ISRAEL THROUGHOUT THEIR GENERATIONS " (Exodus 12:40-42).
Some people have referred to this nighttime commemoration of leaving Egypt as "the Night to be much Observed," which is based upon the King James Bible translation of Exodus 12:42. When God brought Israel out of Egypt, He was delivering them from slavery.
" I am the Lord your God, who brought you out of the land of Egypt, that you should not be their SLAVES; . . . " (Leviticus 26:13).
"And remember that you were a SLAVE in the land of Egypt, and the Lord your God brought you out from there by a mighty hand and by an outstretched arm . . . " (Deuteronomy 5:15).
Before baptism, we are in bondage and slavery to sin as Israel was to Egypt. Our freedom from the bondage of sin comes through the sacrifice of Jesus Christ. During the New Testament Passover service, believers remember and commemorate the death of Jesus Christ that makes spiritual freedom possible. Believers who observe "the Night to be much Observed" celebrate their freedom and deliverance from spiritual Egypt, which is symbolic of sin.
As the Israelites were slaves to the Egyptians, we were slaves of sin.
"Jesus answered them, 'Most assuredly, I say to you, whoever commits sin is a SLAVE TO SIN . . .' " (John 8:34).
When baptized, Christians share in the death of Jesus by being "baptized into His death." When they partake of the Passover each year, they also share in the body and blood (the death) of Jesus Christ (Romans 6:1-3).
On the Night to be much Observed Israel began their new life by walking out of Egypt (Joshua 5:6; Judges 11:16). In like manner, this night pictures the beginning of a Christian's walk in the newness of life, a life committed to walking in obedience to God (Romans 6:4). This night is also a reminder of a Christian's freedom from the slavery of sin, made possible by the sacrifice of Jesus.
"But thanks be to God, that you were the servants of sin, but you have obeyed from the heart that form of doctrine which was delivered to you; 18. And having been delivered from sin, you became the servants of righteousness (Romans 6:17-18).
According to the Bible, Christians are to consider themselves "dead to sin" and strive to obey God (Romans 6:8-11,13).
The Old Testament Passover was a memorial of God passing over the houses of the children of Israel when He killed the firstborn of Egypt. The New Testament Christian Passover is not a memorial of Israel's exodus from Egypt but a memorial of the death of Jesus Christ. Christians eat unleavened bread and drink a small cup of wine in remembrance of Jesus' sacrifice.
"For as often as you eat this bread and drink this cup, you proclaim the Lord’s death till He comes" (1Corinthians 11:26).
The Biblical meaning of Passover for Christians is to celebrate freedom and deliverance from spiritual Egypt, or sin, made possible by the perfect sacrifice of Jesus Christ.