Shayban bin Qays al-Qitbani (may Allah have mercy on him) said: Muhammad bin Mukhallad appointed Sayyiduna Ruwayfi' bin Thabit (may Allah be pleased with him) as his deputy over the lower land (Lower Egypt). Shayban bin Qays said: So we set out with him. Then Sayyiduna Ruwayfi' bin Thabit (may Allah be pleased with him) told me; he said: In the time of the Messenger of Allah (peace and blessings be upon him), one of us would take his brother's emaciated camel on the condition that he would give him half of whatever spoils he gained and keep half himself, so much so that one of us would get the arrowhead and the feathers, and the other the shaft of the arrow. Then Sayyiduna Ruwayfi' (may Allah be pleased with him) said to me: The Messenger of Allah (peace and blessings be upon him) said to me: "O Ruwayfi'! Perhaps your life will be long after me, so tell the people that whoever ties his beard in a knot, or hangs a bowstring around his neck, or cleans himself after relieving himself (istinja) with the dung of his animal or with a bone, then Muhammad (peace and blessings be upon him) is free of him."
Hadith Referenceالمعجم الكبير للطبراني / باب الراء / 4476