Language:
كتاب المغازى
64  
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
(38)
Chapter: Ghazwa of Khaibar
(38)
باب غَزْوَةُ خَيْبَرَ
Sahih al-Bukhari 4214

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 (ﷺ) was there. So I felt shy (to take it then).

حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا شُعْبَةُ‏.‏ وَحَدَّثَنِي عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَهْبٌ، حَدَّثَنَا شُعْبَةُ، عَنْ حُمَيْدِ بْنِ هِلاَلٍ، عَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ ـ رضى الله عنه ـ قَالَ كُنَّا مُحَاصِرِي خَيْبَرَ فَرَمَى إِنْسَانٌ بِجِرَابٍ فِيهِ شَحْمٌ، فَنَزَوْتُ لآخُذَهُ، فَالْتَفَتُّ فَإِذَا النَّبِيُّ صلى الله عليه وسلم، فَاسْتَحْيَيْتُ‏.‏
Reference : Sahih al-Bukhari 4214
In-book reference : Book 64, Hadith 254
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 525
  (deprecated numbering scheme)