Musnad Ahmad 907:209

'Affan narrated to us, Abu 'Awanah narrated to us, 'Uthman ibn 'Abdullah ibn Mawhab narrated to us, from Ja'far ibn Abi Thawr, from Jabir ibn Samurah, who said: I was sitting with the Prophet, peace and blessings of Allah be upon him, when a man came to him and said: "O Messenger of Allah, should we perform ablution after eating mutton?" He said: "If you wish, perform ablution from it, and if you wish, do not perform ablution." He said: "Should we perform ablution after eating camel meat?" He said: "Yes, perform ablution from camel meat." He said: "Should we pray in the resting places of camels?" He said: "No." He said: "Should we pray in the sheepfolds?" He said: "Yes, pray in the sheepfolds."