(18) باب اسْتِحْبَابِ مُبَايَعَةِ الإِمَامِ الْجَيْشَ عِنْدَ إِرَادَةِ الْقِتَالِ وَبَيَانِ بَيْعَةِ الرِّضْوَانِ تَحْتَ الشَّجَرَةِ
The tradition has been narrated on the authority of Sa'id b. Musayyib who learnt it from his father. The latter said:
I had seen the tree. When I came to the spot afterwards, I could not recognise it.
Reference: Sahih Muslim 1859 c
In-book reference: Book 33, Hadith 117
USC-MSA web (English) reference(deprecated numbering scheme): Book 20, Hadith 4589