Ibn ‘Umar (may Allah be pleased with him) reported: Whenever we gave the Messenger of Allah (may Allah's peace and blessings be upon him) pledge of allegiance to listen and obey, he would say to us: "To the best of your ability. [Sahih/Authentic] - [Al-Bukhari ]

كنا إذا بايعنا رسول الله -صلى الله عليه وسلم- على السمع والطاعة، يقول لنا: «فيما استطعتم» رواه البخاري