Musnad Abu Ya'la al-Mawsili 243:67

Sa'id ibn Yahya ibn Sa'id al-Umawi narrated to us, my father narrated to me, Burayd ibn 'Abd Allah ibn Abi Burdah narrated to us, from Abu Burdah, from Abu Musa, who said: We asked the Messenger of Allah, peace and blessings of Allah be upon him, "Which Islam is best?" He said: "He from whose tongue and hand the Muslims are safe."