Sahih Muslim | Book 18 | Chapter 11

Narrated by 'Abd al-Rahman b. 'Uthman al-Taimi
'Abd al-Rahman b. 'Uthman al-Taimi reported that Allah's Messenger (may peace be upon him) forbade taking into custody the stray thing of the pilgrims.

Narrated by Zaid b. Khalid al-Juhani
Zaid b. Khalid al-Juhani reported Allah's Messenger (may peace be upon him) as saying: He who found a stray article is himself led astray if he does not advertise it.