One of the problems which had afflicted the church in Corinth was that of the fornicating brother who was immorally involved with his stepmother. Paul had demanded that this wicked man be excluded from the fellowship of the church (1 Corinthians 5). There may be a passage in Paul’s second letter to this church that relates to this episode.
The apostle writes:
“Sufficient to such a one is this punishment which was inflicted by the many” (2:6).
Most of the older New Testament scholars believed this to be an allusion to the incident in 1 Corinthians 5. It is suggested that the sincere element of the Corinthian church (“the many,” i.e., the majority) followed Paul’s admonition and disfellowshipped the wayward man. Happily, however, as likely indicated by this passage, the punishment was sufficient and the brother was restored (see James Macknight, Apostolical Epistles, pp. 213-214).
You might wish to block off verse 6 and note in your margin: Possible reference to 1 Corinthians 5.
More recent writers think the allusion was to an anti-Paul faction that had been brought under control. In either case, discipline had worked. Moreover, it did not take the entire church to get the job done. There may always be a rebellious minority that refuses to practice discipline. They can answer to God for their lack of brotherly concern.