Musannaf Ibn Abi Shayba 3:5448

Waki’ narrated to us, he said: Ibn Abi Layla narrated to us, from a sheikh who is called Hilal, from Hudhayfah, he said: I asked the Messenger of Allah (peace and blessings of Allah be upon him) about everything, even about smoothing the pebbles. He said: "One [time], or leave it."