Musnad Ahmad 32:2100

'Affan narrated to us, Hammad narrated to us, he said: Thabit informed us, from Anas bin Malik, that the Prophet (peace and blessings of Allah be upon him) had a camel driver who was good at singing (huda'). He was the driver for the men. Anjashah used to drive for the wives of the Prophet (peace and blessings of Allah be upon him). When he drove [the camels], the camels quickened their pace. The Prophet (peace and blessings of Allah be upon him) said: "Woe to you, O Anjashah, drive slowly with the glass vessels."