ENOfficial
Ibn ‘Umar told that when they swore allegiance to God’s Messenger to hear and obey he was saying to them, “In what you are able.” (Bukhari and Muslim.)
Source: sunnah.com
Other translations
Arabic
وَعَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا قَالَ: كُنَّا إِذَا بَايَعْنَا رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَلَى السَّمْعِ وَالطَّاعَةِ يَقُولُ لَنَا: «فِيمَا اسْتَطَعْتُمْ»
sunnah.com