Muwatta Malik 1808
موطأ مالك#1808Sahihحَدَّثَنِي 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 ibn Umar said, "When we took an oath of allegiance with him to hear and obey, the Messenger of Allah, may Allah bless him and grant him peace, said to us, 'In what you are able
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 55:1