On July 9, 2005, al Qaeda second-in-command “Ayman al-Zawahiri sent a letter to an associate of [al Qaeda in Iraq leader Abu Musab al-] Zarqawi’s, which was intercepted by U.S. forces in Iraq in July 2005, urging him to exercise more restraint in his campaign against the Shia: ‘Many of your Muslim admirers amongst the common folk are wondering about your attacks on the Shia.’ Zawahiri also gently advocated an end to Zarqawi’s televised executions: ‘Among the things which the feelings of the Muslim population who love and support you will never find palatable are the scenes of slaughtering the hostages.’ “
– Peter Bergen, The Longest War, Pages 166-167