We are brothers and sisters only in and through Christ
Christianity means community through Jesus Christ and in Jesus Christ. No Christian community is more or less than this. We belong to one another only through and in Jesus Christ. What does that mean? It means first, that a Christian needs others because of Jesus Christ. Second, it means that a Christian comes to others only through Jesus Christ. It means third, that in Jesus Christ we have been chosen from eternity, accepted in time and united for eternity... 

The Christian lives wholly by the truth of God's Word in Jesus Christ. Because he daily hungers and thirsts for righteousness, he daily desires the redeeming Word. In himself he is destitute and dead. Help must come from the outside, and it has come and comes daily and anew in the Word of Jesus Christ, bringing redemption, righteousness, innocence and blessedness.

God's living Word in the witness of our brother and sister
But God has put this Word in to the mouth of others in order that it may be communicated to us. When one person is struck by the Word, he speaks it to others. God has willed that we should seek and find his living Word in the witness of a brother, in the mouth of a man. Therefore, the Christian needs another Christian who speaks God's Word to him. He needs him again and again when he becomes uncertain and discouraged for by himself he cannot help himself without belying the truth. 

He needs his brother and sister as a bearer and proclaimer of the divine word of salvation. He needs his brother and sister solely because of Jesus Christ. And that also clarifies the goal of all Christian community: they meet one another as bringers of the message of salvation. As such, God permits them to meet together and gives them community. Their fellowship is founded solely upon Jesus Christ and this 'alien righteousness'. All we can say, therefore, is: the community of Christians springs solely from the biblical and reformation message of the justification of man through grace alone – this alone is the basis of the longing of Christians for one another.

Without Christ there is discord
Second, a Christian comes to others only through Jesus Christ. Among people there  is strife. 'He is our peace,' says Paul of Jesus. Without Christ there is discord between God and man and between man and man. Christ became the mediator and made peace with God and among men. 

Without Christ we would not know God, we could not call upon him, nor come to him. But without Christ we also could not know our brother, nor could we come to him. The way is blocked by our ego. Christ opened the way to God and to our brother. Now Christians can live with one another in peace – they can become one. But they can continue to do so only by the way of Jesus Christ. Only in Jesus Christ are we one, only through Jesus Christ are we bound together. To eternity he remains the one mediator.

We are members of the Body of Christ
Third, when God's Son took on flesh, he truly and bodily took on, out of pure grace, our being, our nature, ourselves. This was the eternal counsel of the Triune God. Now we are in him. Where he is, there we are too, in the incarnation, on the cross and in his resurrection. We belong to him because we are in him. That is why the Scriptures call us the Body of Christ. 

But if before we could know and wish it, we have been chosen and accepted with the whole Church in Christ, then we also belong to him in eternity with one another. We who live here in fellowship with him will one day be with him in eternal fellowship. 

He who looks upon his brother and sister should know that he and she will be eternally united with him in Christ. Christian community means community in and through Jesus Christ.

Excel in brotherly love 
God himself has undertaken to teach brotherly love – all that men and women can do to add is to remember this divine instruction and the admonition to excel in it more and more. When God was merciful, when he revealed Jesus Christ to us as our Brother, when he won our hearts by his love, this was the beginning or our instruction in divine love. 

When God was merciful to us, we learned to be merciful with our brethren. When we received forgiveness instead of judgment, we too were made ready to forgive our brethren. What God did to us, we then owed to others. The more we received, the more we were able to give – and the more meager our brotherly love, the less we were living by God's mercy and love. Thus God taught us to meet one another as God met us in Christ.

My brother and sister has been redeemed by Christ
The fact that we are brethren only through Jesus Christ is of immeasurable significance. Not only the other person who is earnest and devout, who comes to me seeking brotherhood, must I deal with in fellowship. My brother or sister is rather that other person who has been redeemed by Christ, delivered from sin and called to faith and eternal life. 

Our community with one another consists solely of what Christ has done to both of us. I have community with others and I shall continue to have community only through Jesus Christ. The more genuine and the deeper our community becomes, the more will everything else between us recede, the more clearly and purely will Jesus Christ and his work become the one and only thing that is vital between us. 

Christian community is not an ideal which we must realize – it is rather a reality created by God in Christ in which we may participate.

[Excerpts are from Life Together, Chapter 1 Community, written in German by Dietrich Bonhoeffer in 1937 and originally published in 1939 under the German title Gemeinsames Leben. It was first translated into English in 1954 by John W. Doberstein and published by Harper & Row, London, New York, San Francisco. An updated English translation by James Burtness and Dan Bloesch in Life Together and the Prayerbook of the Bible: Dietrich Bonhoeffer Works, Volume 5, 1996, 2005 by Augsburg Fortress.].

In the seminary at Finkenwalde Bonhoeffer taught the importance of shared life together as disciples of Christ. He was convinced that the renewal of the church would depend upon recovering the biblical understanding of  the communal practices of Christian obedience and shared life. This is where true formation of discipleship could best flourish and mature. Bonhoeffer’s teaching led to the formation of a community house for the seminarians to help them enter into and learn the practical disciplines of the Christian faith in community. 

In 1937 Bonhoeffer completed two books, Life Together and The Cost of Discipleship. They were first published in German in 1939. Both books encompass Bonhoeffer’s theological understanding of what it means to live as a Christian community in the body of Christ.He was arrested by the Gestapo in April 1943. On April 8, 1945 he was hanged by the Gestapo as a traitor in the Flossenburg concentration camp. As he left his cell on his way to execution he said to his companion, "This is the end – but for me, the beginning of life."