Scripture speaks in Matthew 6 and other places on forgiveness as pertains mainly to individuals, but Paul speaks in 2 Corinthians Chapter 2 to the church’s responsibility.
Paul begins the chapter by expressing grief over having to rebuke them in his first letter. In verse 5 he brings up one of the incidents he had rebuked them for from 1 Cor. 5, a man living in sexual sin. Paul had instructed the church in Corinth to remove this man from their congregation, now he tells them it’s time to stop rebuking him, forgive the man, comfort him, and encourage him so that he not be overwhelmed with sorrow.
Note Paul doesn’t specifically tell them to welcome him back into the church yet. Apparently the man had shown sorrow over his actions; perhaps he had even repented or was showing signs of it. Paul, therefore instructs the church to be active in helping restore this man back into the fellowship.
How many times has a church member, even a Christian church member, fallen into sin, and that church (not just a few members, but the church as a whole) never actively seeks to restore and welcome back that member? In verse 11, Paul warns them of the dangers of unforgiveness; it becomes a foothold for Satan.
We should take this warning much more seriously. Satan has stopped churches from growing more often than not because the church refused to forgive and restore a fallen member.