Musnad Ahmad 448:7

Hassan ibn Musa al-Ashyab narrated to us, he said: Ibn Lahi'ah informed us, he said: 'Ayyash ibn 'Abbas narrated to us, from Shuyaym ibn Baytan, he said: Ruwayfi' ibn Thabit narrated to us, he said: One of us in the time of the Messenger of Allah (peace and blessings of Allah be upon him) would take his brother’s camel on the condition that he would give him half of what he gained, and he would have the other half, to the extent that one of us would be allotted the arrowhead and the feathers, and the other the shaft. Then the Messenger of Allah (peace and blessings of Allah be upon him) said to me: "O Ruwayfi', perhaps life will be long for you, so inform the people that whoever ties his beard, or wears a bowstring around his neck, or cleans himself with animal dung or a bone, then Muhammad (peace and blessings of Allah be upon him) is free of him."