Musnad Abu Ya'la al-Mawsili 130:12

Abu al-Rabi' narrated to us, Hammad narrated to us, from 'Abd al-'Aziz ibn Suhayb, from Anas, that the Prophet (may Allah bless him and grant him peace) said: "O Mu'adh." He said: "At your service, O Messenger of Allah." He said: "Give glad tidings to the people that whoever says 'There is no god but Allah' will enter Paradise."