Sayyiduna Sahl bin Abi Hathmah (may Allah be pleased with him) says: I heard the Prophet (peace and blessings be upon him) say on the pulpit: "Avoid the seven major sins." The people remained silent and no one asked anything, so the Prophet (peace and blessings be upon him) said: "Will you not ask me about them? Associating partners with Allah, killing a soul, fleeing from the battlefield, consuming the wealth of an orphan, consuming usury (riba), slandering a chaste woman, and reverting to Bedouin life after the emigration (hijrah)."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5615