Language:
كتاب الكفالة
39  
Kafalah
(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 2294

Narrated `Asim:

I heard Anas bin Malik, "Have you ever heard that the Prophet (ﷺ) said, 'There is no alliance in Islam?' " He replied, "The Prophet (ﷺ) made alliance between Quraish and the Ansar in my house."

حَدَّثَنَا مُحَمَّدُ بْنُ الصَّبَّاحِ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ زَكَرِيَّاءَ، حَدَّثَنَا عَاصِمٌ، قَالَ قُلْتُ لأَنَسٍ رضى الله عنه أَبَلَغَكَ أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ ‏ "‏ لاَ حِلْفَ فِي الإِسْلاَمِ ‏"‏‏.‏ فَقَالَ قَدْ حَالَفَ النَّبِيُّ صلى الله عليه وسلم بَيْنَ قُرَيْشٍ وَالأَنْصَارِ فِي دَارِي‏.‏
Reference : Sahih al-Bukhari 2294
In-book reference : Book 39, Hadith 5
USC-MSA web (English) reference : Vol. 3, Book 37, Hadith 491
  (deprecated numbering scheme)