Sahih Muslim | Book 20 | Hadith Number 4604

Narrated by It has been narrated on the authority of Abdullah b. 'Umar who
It has been narrated on the authority of Abdullah b. 'Umar who said: We used to take oath to the Messenger of Allah (may peace be upon him) 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.