What is the ruling on a married man who commits adultery with a woman from the People of the Book or an idolatress, whether she is married or single?

Adultery is unequivocally forbidden by the Quran, the Sunnah, and scholarly consensus. Allah says: (And do not approach unlawful sexual intercourse. Indeed, it is ever an indecency and is evil as a way.) The Messenger of Allah, peace and blessings be upon him, said: "The adulterer is not a believer while he is committing adultery." Its consequences are dire in this world and the Hereafter, and a Muslim must repent from it. There is no difference in its prohibition whether the woman involved is Christian, Jewish, or idolatrous, married or unmarried.