John Calvin Commentary 2 Corinthians 2:10

"But to whom ye forgive anything, I [forgive] also: for what I also have forgiven, if I have forgiven anything, for your sakes [have I forgiven it] in the presence of Christ;" — 2 Corinthians 2:10 (ASV)

To whom ye forgive. So that he might more readily pacify them, he added his approval to the pardon they extended. “Do not hesitate to forgive: I promise that I will confirm whatever you have done, and I already endorse your decision to forgive.” Secondly, he says that he does this for their sake; and he does so sincerely and cordially. He had already shown how much he desired that the man’s welfare should be considered: he now declares that he willingly grants this to the Corinthians.

Instead of the expression in the sight of Christ, some prefer person, because Paul in that reconciliation was acting in the place of Christ, and in a way represented his person. I am, however, more inclined to understand him as declaring that he forgives sincerely and without any pretense. For he is accustomed to use this phrase to express pure and undisguised integrity. If, however, anyone prefers the former interpretation, it is to be observed that the person of Christ is introduced, because there is nothing that should more strongly incline us to the exercise of mercy.