Sahih Muslim , Book 33, Hadith 132 (In-Book) ⓘ

It has been narrated on the authority of Abdullah b. 'Umar who said: We used to take oath to the Messenger of Allah 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.

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 ‏" ‏ ‏.‏