Sahih Muslim 1857
Sahih Muslim · Book 33: 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
وَحَدَّثَنَا ابْنُ الْمُثَنَّى ، حَدَّثَنَا أَبُو دَاوُدَ ، ح وَحَدَّثَنَاهُ إِسْحَاقُ بْنُ إِبْرَاهِيمَ ، أَخْبَرَنَا النَّضْرُ بْنُ شُمَيْلٍ ، جَمِيعًا عَنْ شُعْبَةَ ، بِهَذَا الإِسْنَادِ مِثْلَهُ .
The same tradition has been handed down through a different chain of transmitters.