What does 1 Corinthians 5:1 mean?

Scripture was originally written without chapter and verse divisions. While this verse seems to take a turn from the end of 1 Corinthians 4, it builds on Paul's warning that he will come to them with the rod of correction if necessary.

Paul had received a report about a serious sin being committed by someone belonging to the group of Corinthian Christians. This report may have come from visitors to Paul in Ephesus, either Chloe's people (1 Corinthians 1:11) or Stephanas, Fortunatus, and Achaicus (1 Corinthians 16:17) or both.

The report was this: a man in the Corinthian church had either married or was having an affair with his father's wife. Paul's phrasing that the man "has" this woman indicates a present-tense, ongoing sexual relationship of some kind. It seems clear the woman was not the man's biological mother, but someone who was or had been married to his father.

Paul describes this as sexual immorality. The Greek word for "sexual immorality," porneia, covered all forbidden sexual activity, including incestuous sex with a relative, whether biological, adopted, or by marriage. New Testament teaching is clear that any sex outside of heterosexual marriage is sinful for Christians (2 Corinthians 12:21; Galatians 5:19; Ephesians 5:3; Colossians 3:5; 1 Thessalonians 4:3).

Beyond that, sex with your father's wife was a crime for Jews who followed the law of Moses, punishable by death (Leviticus 20:11). It was even a serious violation of the otherwise very lax moral standards of the Greek and Roman culture. The following verses will make clear that Paul's outrage has as much to do with the Corinthian church's response to this sin among them—or lack of a response—as it does with the sin itself.