Only because of Jesus

The source of the disciple's life lies exclusively in his fellowship with Jesus Christ. He possesses his righteousness only within that association, never outside it. That is why his righteousness can never become an objective criterion to be applied at will. He is a disciple not because he possesses a new standard, but only because of Jesus Christ, the Mediator and very Son of God. That is to say, his righteousness is hidden from himself in fellowship with Jesus. He cannot, as he could once, be a detached observer of himself and judge himself, for he can only see Jesus, and be seen by Him, judged by Him, and reprieved by Him. It is not an approved standard of righteous living that separates a follower of Christ from the unbeliever, but it is Christ who stands between them.

Christians always see other men as brethren to whom Christ comes; they meet them only by going to them with Jesus. Disciple and non-disciple can never encounter each other as free men, directly exchanging their views and judging one another by objective criteria. No, the disciple can meet the non-disciple only as a man to whom Jesus comes.

Here alone Christ's fight for the soul of the unbeliever, His call, His love, His grace and His judgment comes into its own. Discipleship does not afford us a point of vantage from which to attack others; we come to them with an unconditional offer of fellowship, with the single-mindedness of the love of Jesus.

When we judge other people we confront them in a spirit of detachment, observing and reflecting as it were from the outside.
But love has neither time nor opportunity for this. If we love, we can never observe the other person with detachment, for he is always and at every moment a living claim to our love and service.

But does not the evil in the other person make me condemn him just for his own good, for the sake of love?

Here we see the depth of the dividing line. Any misguided love for the sinner is ominously close to the love of sin. But the love of Christ for the sinner in itself is the condemnation of sin, is His expression of extreme hatred of sin.

The disciples are to love unconditionally. Thus they may effect what their own divided and judiciously and conditionally offered love never could achieve, namely the radical condemnation of sin.

If the disciples make judgments of their own, they set up standards of good and evil. But Jesus Christ is not a standard which I can apply to others.

Christian love sees the fellow-man under the cross and therefore sees with clarity.

There is only one judgment, one law, and one grace. Henceforth the disciple will look upon other men as forgiven sinners who owe their lives to the love of God. ‘This is the law and the prophets’—for this is none other than the supreme commandment:

To love God above all things,
and our neighbors as ourselves.

— Dietrich Bonhoeffer, The Cost of Discipleship, Book 2, Chapter 18