Abu Bekr Command to the Saracens

[Prior to the conquest of Syria, Mohammed's uncle, Abu Bekr gave the following order] "...When you fight the battles of the Lord, acquit yourselves like men, without turning your backs; but let not your victory be stained with the blood of women or children. Destroy no palm-trees, nor burn any fields of corn. Cut down no fruit-trees, nor do any mischief to cattle, only such as you kill to eat. When you make any covenant or article, stand to it, and be as good as your word. As you go on, you will find some religious persons who live retired in monasteries, and propose to themselves to serve God that way: let them alone, and neither kill them nor destroy their monasteries: And you will find another sort of people, that belong to the synagogue of Satan, who have shaven crowns; be sure you cleave their skulls, and give them no quarter till they either turn Mahometans or pay tribute."

Gibbon, Edward, The History of the Decline and Fall of the Roman Empire, 6 vols., London: A. Strahan and T. Cadell, 1788, v. 5, p. 297.