Musnad Abu Ya'la al-Mawsili 147:21

Muhammad ibn Bashar al-'Abdi narrated to us, Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Abu Hamzah, our neighbor, who narrated from Anas ibn Malik, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said to Mu'adh ibn Jabal: "Know that whoever testifies that there is no god but Allah will enter Paradise."