Matthew Henry Commentary 2 Corinthians 2:5-11

"But if any hath caused sorrow, he hath caused sorrow, not to me, but in part (that I press not too heavily) to you all. Sufficient to such a one is this punishment which was [inflicted] by the many; so that contrariwise ye should rather forgive him and comfort him, lest by any means such a one should be swallowed up with his overmuch sorrow. Wherefore I beseech you to confirm [your] love toward him. For to this end also did I write, that I might know the proof of you, whether ye are obedient in all things. 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." — 2 Corinthians 2:5-11 (ASV)

The apostle desires them to receive the person who had done wrong back into their communion, because he was aware of his fault and greatly afflicted by his punishment. Even sorrow for sin should not render someone unfit for other duties or drive them to despair.

Not only was there a danger lest Satan might gain an advantage by tempting the penitent to negative thoughts about God and religion, and so drive him to despair; but there was also a danger to the churches and the ministers of Christ, by Satan giving Christians a bad reputation as unforgiving, thereby causing divisions and hindering the success of the ministry.

In this, as in other things, wisdom should be used, so that the ministry may not be blamed for indulging sin on the one hand, or for excessive severity towards sinners on the other hand. Satan has many plans to deceive, and knows how to exploit our mistakes.