رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 663
The Book of Miscellany
Obligation of Obedience to the Ruler in what is Lawful and Prohibition of Obeying them in what is Unlawful
وعنه قَالَ: كُنَّا إِذَا بَايَعْنَا رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَلَى السَّمْعِ وَالطَّاعَةِ يَقُولُ لَنَا: “فِيمَا اسْتَطَعْتُمْ” ((مُتَّفَقٌ عَلَيْهِ))
Ibn 'Umar (May Allah be pleased with them) reported: Whenever we took a pledge of allegiance to Messenger of Allah (ﷺ) to hear and obey, he (ﷺ) would say to us, "As far as you are capable of." [Al-Bukhari and Muslim].
Riyad as-Salihin, 663