صَحِيحُ مُسْلِمٍ
Sahih Muslim 1860 b
The Book on Government
It is recommended for the army to swear allegiance to the ruler when intending to fight, and an account of Bay'at Ar-Ridwan beneath the tree
وَحَدَّثَنَاهُ إِسْحَاقُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا حَمَّادُ بْنُ مَسْعَدَةَ، حَدَّثَنَا يَزِيدُ، عَنْ سَلَمَةَ، بِمِثْلِهِ .
The above tradition has also been handed down through a different chain of transmitters.
Sahih Muslim, 1860 bSahihصحيح