Musnad Ahmad 32:598

'Abd al-Samad narrated to us, he said: Hammad narrated to us, from Thabit, from Anas, who said: The Abyssinians were performing a rhythmic dance (*yazfunun*) before the Messenger of Allah, may Allah bless him and grant him peace, and they were dancing and saying: "Muhammad is a righteous servant." The Messenger of Allah, may Allah bless him and grant him peace, said: "What are they saying?" They said: "They are saying: Muhammad is a righteous servant."