Here in 2 Corinthians 2, Paul is making reference to a church discipline situation that happened within this ancient congregation. It was a vile situation. A man had carried on an affiar with his step-mother. It was public. It was bad. It was a mess!
The church did the right thing. They didn't overlook the sin. They didn't ignore it. They dealt with it. They followed the commands of our Lord in Matthew 18 and the ecclesiastical rod bore the fruit of repentance! That's good news!!
The whole purpose of church discipline is to see a brother or sister restored. It is to bring the wayward sheep home. It is not for shunning but for shepherding. It is for our good and for God's glory. Paul is making sure that the flock of Corinth understand this.
So, now what do they do? They need to "forgive him and comfort him, lest somehow such a one be overwhelmed by excessive sorrow." This brother has blown it and this brother has been restored and our enemy, the devil (who is the father of lies and the accuser of the brethren) would like nothing more than to drive this repentant one to deep and dark despair. Satan HATES repentance and he is a sneaky and coniving enemy who will seize any opportunity to steal, kill, and destroy. What better way for him to have success in his dastardly deeds than to involve the church in them!! Paul recognizes this and even exhorts them regarding the fact in verse 11. He tells them to forgive this wounded lamb "in order that no advantage be taken of us by Satan; for we are not ignorant of his schemes." Let us not be ignorant of his schemes either!
Oh I pray that we are treating them as Christ has treated us - with forgiveness and comfort. Let not the restored one be overwhelmed by despairing condemnation. Instead, "reaffirm your love for him." Christ is full of compassion for those who truly repent, may we be likewise.