Sahih Bukhari, Chapter: Wills and Testaments (Wasaya)

The Prophet (SAW) said, "Avoid the seven great destructive sins." The people enquire, "O Allah's Apostle (SAW)! What are they? "He said, "(1) To join others in worship along with Allah, (2) to practice sorcery, (3) to kill the life which Allah has forbidden except for a just cause, (according to Islamic law), (4) to eat up Riba (usury), (5) to eat up an orphan's wealth, (6) to show one's back to the enemy and fleeing from the battlefield at the time of fighting, (7) and to accuse, chaste women, who never even think of anything touching chastity and are good believers.