Translation
(39) Kafalah
كتاب الكفالة
(2) Chapter: The Statement of Allah jala jalaaluhu:"... To those also with whom you have made a pledge, give them their due portion by Wasiya..."
(2) بَابُ قَوْلِ اللَّهِ تَعَالَى: {وَالَّذِينَ عَاقَدَتْ أَيْمَانُكُمْ فَآتُوهُمْ نَصِيبَهُمْ}
Sahih al-Bukhari 2293 

Narrated Anas:

`Abdur-Rahman bin `Auf came to us and Allah's Messenger (ﷺ) established a bond of brotherhood between him and Sa`d bin Rabi`a.

حَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ جَعْفَرٍ، عَنْ حُمَيْدٍ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ قَدِمَ عَلَيْنَا عَبْدُ الرَّحْمَنِ بْنُ عَوْفٍ فَآخَى رَسُولُ اللَّهِ صلى الله عليه وسلم بَيْنَهُ وَبَيْنَ سَعْدِ بْنِ الرَّبِيعِ‏.‏
Reference : Sahih al-Bukhari 2293
In-book reference : Book 39, Hadith 4
USC-MSA web (English) reference : Vol. 3, Book 37, Hadith 490
  (deprecated numbering scheme)