From Sahih Bukhari (Hadith 3005):
Narrated Abu Bashir Al-Ansari:That he was in the company of Allah's Messenger (ﷺ) on some of his journeys. (The sub-narrator `Abdullah adds, "I think that Abu Bashir also said, 'And the people were at their sleeping places.") Allah's Apostle sent a messenger ordering: "There shall not remain any necklace of string or any other kind of necklace round the necks of camels except it is cut off
Reference: Bukhari 3005