Language:
كتاب الرهن
48  
Mortgaging
(1)
Chapter: The Statement of Allah Taa'la: "And if you are on a journey and cannot find a scribe, then let there be a pledge taken..."
(1)
باب فِي الرَّهْنِ فِي الْحَضَرِ
Sahih al-Bukhari 2508

Narrated Anas:

No doubt, the Prophet (ﷺ) mortgaged his armor for barley grams. Once I took barley bread with some dissolved fat on it to the Prophet (ﷺ) and I heard him saying, "The household of Muhammad did not possess except a Sa (of food grain, barley, etc.) for both the morning and the evening meals although they were nine houses."

حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هِشَامٌ، حَدَّثَنَا قَتَادَةُ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ وَلَقَدْ رَهَنَ النَّبِيُّ صلى الله عليه وسلم دِرْعَهُ بِشَعِيرٍ، وَمَشَيْتُ إِلَى النَّبِيِّ صلى الله عليه وسلم بِخُبْزِ شَعِيرٍ وَإِهَالَةٍ سَنِخَةٍ، وَلَقَدْ سَمِعْتُهُ يَقُولُ ‏ "‏ مَا أَصْبَحَ لآلِ مُحَمَّدٍ صلى الله عليه وسلم إِلاَّ صَاعٌ، وَلاَ أَمْسَى ‏"‏‏.‏ وَإِنَّهُمْ لَتِسْعَةُ أَبْيَاتٍ‏.‏
Reference : Sahih al-Bukhari 2508
In-book reference : Book 48, Hadith 1
USC-MSA web (English) reference : Vol. 3, Book 45, Hadith 685
  (deprecated numbering scheme)