"Is not the cup of thanksgiving for which we give thanks a participation in the blood of Christ? And is not the bread that we break a participation in the body of Christ? Because there is one loaf, we, who are many, are one body, for we all partake of the one loaf." 1 Corinthians 10:16,17
The purpose of Christ's death on the cross was to pay the price necessary to reconcile mankind to God and mankind to one another. The cross represents the redemptive power of Christ's sacrifice that purchased man for God (vertical fellowship - koinonia) and man for one another (horizontal fellowship - koinonia). In other words, it cost Jesus His life to make us one with God and one with one another!
Through faith in Christ the believer is joined to God:
"But he who unites himself with the Lord is one with him in spirit." 1 Corinthians 6:17
And to one another:
"The body is a unit, though it is made up of many parts; and though all its parts are many, they form one body. So it is in Christ. For we were all baptised by one Spirit into one body - whether Jews or Greeks, slave or free - and we were all given one Spirit to drink." 1 Corinthians 12:12,13
The mystery of Christ, which was not made known to men in other generations as it has now been revealed by the Spirit to God's holy apostles and prophets, is that through the gospel the Gentiles are heirs together with Israel, members together of one body, and sharers together in the promise in Christ Jesus (Ephesians 3:4-6).
The believer is not a saved individual but one who has been saved into the community of believers - the Church. Peter writes,
"Once you were not a people, but now you are the people of God." 1 Peter 2:10
The believer has a new identity in Christ. The old identity that was independent, self-centred and separated from God and His people has been replaced with a new identity that is dependent on God, considerate (mindful of others) and joined to God and His people.
Holy Communion, also called the Eucharist or the Lord's supper, is the act of remembering Christ's death and the significance of His sacrifice. Having seen that Christ died to reconcile man to God and to one another we can understand Paul's instructions to the Corinthian church about how they should take communion together. He writes,
"When you come together, it is not the Lord's Supper you eat, for as you eat, each of you goes ahead without waiting for anybody else. One remains hungry, another gets drunk. Don't you have homes to eat and drink in? Or do you despise the church of God?" 1 Corinthians 11:20-22
When believers do not consider one another and love one another, they despise and dishonour the Church. Paul writes,
"Therefore, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord. A man ought to examine himself before he eats of the bread and drinks of the cup. For anyone who eats and drinks without recognising the body of the Lord eats and drinks judgment on himself. That is why many among you are weak and sick, and a number have fallen asleep." 1 Corinthians 11:27-30
"Recognising the body of the Lord" means honouring the Body of Christ, the Church. Paul is saying that before believers eat the bread and drink the cup of the Lord, they must first consider one another. Taking communion together honours what Christ has purchased with His blood - union with God and union with one another.
We cannot have fellowship with Christ and ignore our relationships with one another - that is to despise the Church. As those purchased with the blood of Jesus, we must "make every effort to keep the unity of the Spirit through the bond of peace. There is one body and one Spirit." (Ephesians 4:3,4)
We cannot produce the unity purchased by the blood of Jesus but we are responsible to keep it!
I am convinced that when the people of God have revelation of their new identity in Christ, as the Church of God, and of what it cost Jesus to purchase men for God, that they will make a commitment to live in unity with one another. It is my prayer that the world would see the glory of the Church as we live in communion with God and one another. I praise God that on that great day when the times will have reached their fulfillment that we will hear "every creature in heaven and on earth and under the earth and on the sea, and all that is in them, singing: 'To him who sits on the throne and to the Lamb be praise and honour and glory and power, for ever and ever!'" And why will we hear every creature singing? Because Christ was slain, and with His blood He purchased men for God from every tribe and language and people and nation. He has made them to be a kingdom and priests to serve our God, and they will reign on the earth" (see Revelation 5:9-14).
"Now to him who is able to do immeasurably more than all we ask or imagine, according to his power that is at work within us, to him be glory in the church and in Christ Jesus throughout all generations for ever and ever! Amen." Ephesians 3:20,21