Musnad Ahmad 30:2358

Abu Mu'awiyah and Waki' narrated to us, they said: Al-A'mash narrated to us, from Abu Hazim, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If a foreleg were gifted to me, I would accept it, and if I were invited to a trotter, I would answer." Waki' said in his narration: "If a foreleg were gifted to me."