Sahih Bukhari Volume 4, Book 52, Hadith Number 249.

Narated By Abu Bashir Al-Ansari : That he was in the company of Allah’s Apostle 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.”