Excerpt from Life Together

In confession the break-through to community takes place. Sin demands to have a man by himself. It withdraws him from the community. The more isolated a person is, the more destructive will be the power of sin over him, and the more deeply he becomes involved in it, the more disastrous is his isolation. Sin wants to remain unknown. It shuns the light. In the darkness of the unexpressed it poisons the whole being of a person. This can happen even in the midst of a pious community. In confession the light of the Gospel breaks into the darkness and seclusion of the heart. The sin must be brought into the light. The unexpressed must be openly spoken and acknowledged. All that is secret and hidden is made manifest. It is a hard struggle until the sin is openly admitted. But God breaks gates of brass and bars of iron (Ps. 107:16).

Since the confession of sin is made in the presence of a Christian brother, the last stronghold of self-justification is abandoned. The sinner surrenders; he gives up all his evil. He gives his heart to God, and he finds the forgiveness of all his sin in the fellowship of Jesus Christ and his brother.

The expressed, acknowledged sin has lost all its power. It has been revealed and judged as sin. It can no longer tear the fellowship asunder. Now the fellowship bears the sin of the brother. He is no longer alone with his evil for he has cast off his sin in confession and handed it over to God. It has been taken away from him. Now he stands in the fellowship of sinners who live by the grace of God in the Cross of Jesus Christ. Now he can be a sinner and still enjoy the grace of God. He can confess his sins and in this very act find fellowship for the first time. The sin concealed separated him from the fellowship, made all his apparent fellowship a sham; the sin confessed has helped him to find true fellowship with the brethren in Jesus Christ. 

Moreover, what we have said applies solely to confession between two Christians. A confession of sin in the presence of all the members of the congregation is not required to restore one to fellowship with the whole congregation. I meet the whole congregation in the one brother to whom I confess my sins and who forgives my sins. In the fellowship I find with this one brother I have already found fellowship with the whole congregation. In this matter no one acts in his own name nor by his own authority, but by the commission of Jesus Christ. This commission is given to the whole congregation and the individual is called merely to exercise it for the congregation. If a Christian is in the fellowship of confession with a brother he will never be alone again, anywhere.

Bonhoeffer, Dietrich. Life Together: The Classic Exploration of Christian Community. New York: HarperOne, 2009. pp. 112 – 113.