Charles Ellicott Commentary 1 Corinthians 5:1

"It is actually reported that there is fornication among you, and such fornication as is not even among the Gentiles, that one [of you] hath his father`s wife." — 1 Corinthians 5:1 (ASV)

It is reported commonly.—Better, There is absolutely said to be fornication among you, and such fornication as is not even among the Gentiles. All the best manuscripts omit the word “named.” The force of the statement is that the fornication was of such a kind (with a stepmother) that even the Gentile world, immoral as it was, regarded it with disgust, and how infinitely worse, then, was it to find such tolerated among Christians, whose moral standard ought to be much higher.

One should have his father’s wife.—The word “have” used here always implies actual marriage in the New Testament. It is, therefore, probable that she had been divorced from his father. The expression “his father’s wife” is the Hebrew way of saying stepmother. St. Chrysostom suggests, “He did not say his ‘stepmother,’ but ‘his father’s wife,’ to strike much more severely”; but St. Paul probably used the Hebrew phrase instead of the ordinary Greek word for “stepmother,” as it was in this phraseology that such a union was forbidden by the law of Moses (Leviticus 18:8).