Musannaf Ibn Abi Shayba 28:969

Mu'awiyah ibn Hisham narrated to us, he said: Malik ibn Anas narrated to us, from Abdullah ibn Abi Bakr, from Abbad ibn Tamim, from Abu Bashir al-Ansari, who said: We were with the Prophet, peace and blessings of Allah be upon him, on one of his journeys. He sent a messenger [saying]: "Let there not remain any necklace of bowstring on the neck of a camel except that it is cut."