Musnad Ahmad 448:11

Yahya ibn Ghaylan narrated to us, he said: Al-Mufaddal narrated to us, he said: Ayyash ibn Abbas narrated to me, that Shuyaym ibn Baytan informed him that he heard Shayban al-Qatabani saying: Maslamah ibn Mukhallad appointed Ruwayfi’ ibn Thabit al-Ansari as governor over the lower land. He said: So we traveled with him. He said: The Messenger of Allah (peace and blessings of Allah be upon him) said to me: "O Ruwayfi’, perhaps life will be prolonged for you after me. So inform the people that whoever ties his beard, or wears a bowstring (as a necklace), or cleans himself (after relieving himself) with the dung of an animal or with a bone, then Muhammad (peace and blessings of Allah be upon him) is innocent of him."