Christ's blood is the only blood God allows us to consume - indeed, we must consume it, for it is the guarantee of eternal life. Jesus explains this in John 6:53-57, which I will read:
The eating and drinking relate to something that is ongoing rather than something that is past. Jesus has already fulfilled the sin offering, and the individual would not eat or drink of it anyway. But the spiritual life - the abundance - pictured in the bread and wine is something we experience as we look forward to the future with great hope because of the covenant and what God promises to do within it. The verbs, eat, drink, eats, drinks, abides, and feeds in this passage are in the present tense, meaning that we do them on a continual basis. Our eating and drinking of Christ describe our relationship with Him.
John 6:57 in J.B. Phillips' translation reads, The man who eats [M]y body and drinks [M]y blood shares [M]y life and I share his. The life He gives us imparts the true well-being and fulfillment that this world cannot give. The Passover is a commemoration of the abundant, eternal life that God has graciously made available to us, which will find its culmination when the Passover is fulfilled at Christ's return.
The implication is food that gives life and drink that gives life.
Abides means lives in, or dwells in. It has the force, or the thrust, of continuing in. In other words, He is telling us here that if we are going to continue to live in Him (from the time that we, by faith, accept His blood and repent), then we are going to have to keep renewing. That is, keep eating of His bread and eating of His blood - because that gives life. Do you see the symbolism that is here? It is very clear.
I think that we all understand that repentance and accepting the blood of Jesus Christ begins the process that leads to salvation. So, in verses 55-57, He is affirming to us that salvation (which is the completion of the process) comes as a result of the continuance of the relationship through the reaffirmation of the covenant - that is, through Passover.
Jesus Christ's body is a multi-faceted symbol. Sometimes Christ's body is a symbol of His death, but at other times it is a symbol of life. So, it says here that the Passover bread represents Christ's body. When Jesus uses bread as a symbol for His body, it is a symbol of life, even eternal life. We won't turn to it, but John 6 explains this symbol very clearly. There, Jesus speaks of bread that endures to everlasting life. He speaks of the bread of God, the bread of life, and the living bread. When Jesus says that He is the living bread (John 6:51), it means that His flesh is not merely something that leads to eternal life, but He indicates a body that is alive. As we partake of the bread, we become one with the living Savior.
