Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 525
Narrated 'Abdullah bin Mughaffal:
While we were besieging Khaibar, a person threw a leather container containing some fat and I ran to take it. Suddenly I looked behind, and behold! The Prophet was there. So I felt shy (to take it then).