Mukhtasar Bukhari

Abu Huraira (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The adulterer, at the time of committing adultery, is not a believer; and the one who drinks alcohol, at the time of drinking, is not a believer; and the thief, at the time of stealing, is not a believer."