Musannaf Ibn Abi Shayba 1:514

Ubayd Allah ibn Musa narrated to us, from Isra'il, from Ash'ath ibn Abi al-Sha'tha', from Ja'far ibn Abi Thawr, from Jabir ibn Samurah, who said: The Messenger of Allah (may Allah bless him and grant him peace) commanded us to perform ablution (wudu) after eating camel meat, and not to perform ablution after eating mutton.