حَدَّثَنِي مَالِكٌ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، قَالَ كُنَّا إِذَا بَايَعْنَا رَسُولَ اللَّهِ صلى الله عليه وسلم عَلَى السَّمْعِ وَالطَّاعَةِ يَقُولُ لَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ فِيمَا اسْتَطَعْتُمْ ‏"‏ ‏.‏

Malik related to me from Abdullah ibn Dinar that Abdullah ibnUmar said, "When we took an oath of allegiance with him to hear andobey, the Messenger of Allah, may Allah bless him and grant him peace,said to us, 'In what you are able.' " Translation Not Available

Book Ref: Muwatta Imam Malik Book 55 Hadith 1811
Web Ref:  Muwatta Imam Malik Book 55 Hadith 1