Sahih Muslim 1867
Sahih Muslim · Book 33: The Book on Government · Oath of allegiance pledging to hear and obey as much as possible
It has been narrated on the authority of Abdullah b. 'Umar who said:
حَدَّثَنَا يَحْيَى بْنُ أَيُّوبَ ، وَقُتَيْبَةُ ، وَابْنُ، حُجْرٍ - وَاللَّفْظُ لاِبْنِ أَيُّوبَ - قَالُوا حَدَّثَنَا إِسْمَاعِيلُ، - وَهُوَ ابْنُ جَعْفَرٍ - أَخْبَرَنِي عَبْدُ اللَّهِ بْنُ دِينَارٍ ، أَنَّهُ سَمِعَ عَبْدَ اللَّهِ بْنَ عُمَرَ ، يَقُولُ كُنَّا نُبَايِعُ رَسُولَ اللَّهِ صلى الله عليه وسلم عَلَى السَّمْعِ وَالطَّاعَةِ يَقُولُ لَنَا " فِيمَا اسْتَطَعْتَ " .
We used to take oath to the Messenger of Allah (ﷺ) that we would listen to and obey his orders. He would tell us (to say in the oath): As far as it lies in my power.