Musannaf Ibn Abi Shayba 3:4783

Waki' narrated to us, he said: Sufyan narrated to us, from Sa'd ibn Ibrahim, from Nafi' ibn Jubayr ibn Mut'im, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I am a man who has become heavy (fleshy/corpulent), so do not hasten before me in standing, nor in prostration."