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; that no advantage may be gained over us by Satan: for we are not ignorant of his devices.

Titus had informed Paul of the successful issue of the order of discipline enforced upon the incestuous man, only with the exception that some of the church seemed unwilling to forgive and reinstate him. Paul added the record of his own forgiveness of the man's sin, "in the presence of Christ" as an added inducement to making his forgiveness and reinstatement complete.

His devices ... The device of Satan which surfaces in this paragraph is that of a super-piety that will not forgive offenders even when they have put away their sin, repented, and asked forgiveness. This device is still being used by the devil.