It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The adulterer, when he commits adultery, is not a believer; the thief, when he steals, is not a believer; and the plunderer, when he plunders, is not a believer."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11573