Language:
كتاب المغازى
64  
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
(35)
Chapter: The Ghazwa of Al-Hudaibiya
(35)
باب غَزْوَةِ الْحُدَيْبِيَةِ
Sahih al-Bukhari 4153

Narrated Qatada:

I said to Sa`id bin Al-Musaiyab, "I have been informed that Jabir bin `Abdullah said that the number (of Al-Hudaibiya Muslim warriors) was 1400." Sa`id said to me, "Jabir narrated to me that they were 1500 who gave the Pledge of allegiance to the Prophet (ﷺ) on the day of Al-Hudaibiya.'

حَدَّثَنَا الصَّلْتُ بْنُ مُحَمَّدٍ، حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، عَنْ سَعِيدٍ، عَنْ قَتَادَةَ، قُلْتُ لِسَعِيدِ بْنِ الْمُسَيَّبِ بَلَغَنِي أَنَّ جَابِرَ بْنَ عَبْدِ اللَّهِ، كَانَ يَقُولُ كَانُوا أَرْبَعَ عَشْرَةَ مِائَةً‏.‏ فَقَالَ لِي سَعِيدٌ حَدَّثَنِي جَابِرٌ كَانُوا خَمْسَ عَشْرَةَ مِائَةً الَّذِينَ بَايَعُوا النَّبِيَّ صلى الله عليه وسلم يَوْمَ الْحُدَيْبِيَةِ‏.‏

تَابَعَهُ أَبُو دَاوُدَ حَدَّثَنَا قُرَّةُ عَنْ قَتَادَةَ

Reference : Sahih al-Bukhari 4153
In-book reference : Book 64, Hadith 197
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 474
  (deprecated numbering scheme)