Sahih Bukhari
Punishment of Disbelievers at War with Allah and His Apostle
Volume: 008 / Book Number: 082 / Hadith Number: 840
Narrated Abu Huraira:
The Prophet said, "Avoid the seven great destructive sins." They (the people!) asked, "O Allah's Apostle! What are they?" He said, "To join partners in worship with Allah; to practice sorcery; to kill the life which Allah has forbidden except for a just cause (according to Islamic law); to eat up usury (Riba), to eat up the property of an orphan; to give one's back to the enemy and freeing from the battle-field at the time of fighting and to accuse chaste women who never even think of anything touching chastity and are good believers."