For what have I to do ...? — The Apostle in this verse at once explains the grounds of the limitation of his remarks to Christians, and seems to hint also, by the form of expression here, that the Corinthian Church ought to have been able to have understood his remarks as only applicable to themselves and not to the heathen.
Them also that are without. — The heathen. It was a common form of expression amongst the Jews to designate the Gentile world (Mark 4:11).
Do not ye judge them that are within? — As the Christian Church could sit in judgment only on its own members, so they should have concluded that only on them had St. Paul passed judgment.