(18) باب اسْتِحْبَابِ مُبَايَعَةِ الإِمَامِ الْجَيْشَ عِنْدَ إِرَادَةِ الْقِتَالِ وَبَيَانِ بَيْعَةِ الرِّضْوَانِ تَحْتَ الشَّجَرَةِ
It has been narrated (through a different chain of transmitters) on the authority of Salim b. al-Ja'd who said:
I asked Jabir: How many were you on the Day of Hudaibiya? He said: One thousand and four hundred.
Reference: Sahih Muslim 1856 h
In-book reference: Book 33, Hadith 111
USC-MSA web (English) reference(deprecated numbering scheme): Book 20, Hadith 4583