Abu Bashir al-Ansari (may Allah be pleased with him) was with the Prophet (peace and blessings be upon him) on one of his journeys. He says that the Messenger of Allah (peace and blessings be upon him) sent out a messenger. Abdullah bin Abi Bakr (may Allah have mercy on him) says: I think that the people were sleeping in their resting places when the Prophet (peace and blessings be upon him) said: "Let no necklace of bowstring, or any other necklace, remain on the necks of the camels; cut them off." Imam Malik (may Allah have mercy on him) says: I think this was because of the evil eye.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10329