Language:
كتاب مناقب الأنصار
63  
Merits of the Helpers in Madinah (Ansaar)
(46)
Chapter: The arrival of the Prophet (saws) at Al-Madina
(46)
باب مَقْدَمِ النَّبِيِّ صلى الله عليه وسلم وَأَصْحَابِهِ الْمَدِينَةَ
Sahih al-Bukhari 3930

Narrated `Aisha:

The day of Bu'ath was a day (i.e. battle) which Allah caused to take place just before the mission of His Apostle so that when Allah's Messenger (ﷺ) came to Medina, they (the tribes) had divided (into hostile groups) and their nobles had been killed; and all that facilitated their conversion to Islam.

حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ قَالَتْ كَانَ يَوْمُ بُعَاثٍ يَوْمًا قَدَّمَهُ اللَّهُ عَزَّ وَجَلَّ لِرَسُولِهِ صلى الله عليه وسلم، فَقَدِمَ رَسُولُ اللَّهِ صلى الله عليه وسلم الْمَدِينَةَ وَقَدِ افْتَرَقَ مَلَؤُهُمْ، وَقُتِلَتْ سَرَاتُهُمْ فِي دُخُولِهِمْ فِي الإِسْلاَمِ‏.‏
Reference : Sahih al-Bukhari 3930
In-book reference : Book 63, Hadith 155
USC-MSA web (English) reference : Vol. 5, Book 58, Hadith 267
  (deprecated numbering scheme)