Musnad Ahmad 448:0

It was narrated from Ruwayfi‘ ibn Thabit al-Ansari that the Messenger of Allah (ﷺ) said: "O Ruwayfi‘, perhaps you will live for a long time after me, so tell the people that whoever ties his beard, or wears a string around his neck as a talisman, or cleans himself after relieving himself with animal dung or a bone, then Muhammad has nothing to do with him."