Musnad Abu Ya'la al-Mawsili 150:263

Ahmad ibn Ibrahim Abu Abdullah al-Nukri narrated to us, Abd al-Rahman narrated to us, from Sufyan, from al-A'mash, from Abdullah ibn Murrah, from Abdullah, from the Prophet, may God bless him and grant him peace, who said: "By God, other than whom there is no god, the blood of a Muslim man who testifies that there is no god but God and that I am the Messenger of God is not lawful."