Sahih Bukhari Volume 5, Book 59, Hadith Number 474.

Narrated By 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 on the day of Al-Hudaibiya.”