ʿAbdullah Bin ʿUmar wrote to ʿAbdul Malik bin Marwan, swearing allegiance to him: 'I swear allegiance to you in that I will listen and obey what is in accordance with the Laws of Allah and the Tradition of His Apostle as much as I can.'  

بِالسَّمْعِ وَالطَّاعَةِ عَلَى سُنَّةِ اللَّهِ وَسُنَّةِ رَسُولِهِ فِيمَا اسْتَطَعْتُ  

Malik related to me from Abdullah ibn Dinar that Abdullah ibn Umar wrote to Abd al-Malik ibn Marwan, making an oath of allegiance. He wrote, "In the name of Allah, the Merciful, the Compassionate. To the slave of Allah, Abd al-Malik, the amir al-muminin, Peace be upon you. I praise Allah to you. There is no god but Him. I acknowledge your right to my hearing and my obedience according to the sunna of Allah and the sunna of His Prophet, in what I am able."  

أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَتَبَ إِلَى عَبْدِ الْمَلِكِ بْنِ مَرْوَانَ يُبَايِعُهُ فَكَتَبَ إِلَيْهِ بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ أَمَّا بَعْدُ لِعَبْدِ اللَّهِ عَبْدِ الْمَلِكِ أَمِيرِ الْمُؤْمِنِينَ سَلاَمٌ عَلَيْكَ فَإِنِّي أَحْمَدُ إِلَيْكَ اللَّهَ الَّذِي لاَ إِلَهَ إِلاَّ هُوَ وَأُقِرُّ لَكَ بِالسَّمْعِ وَالطَّاعَةِ عَلَى سُنَّةِ اللَّهِ وَسُنَّةِ رَسُولِهِ فِيمَا اسْتَطَعْتُ  

[Machine] When we used to pledge allegiance to the Messenger of Allah ﷺ regarding listening and obeying, he would say to us, "Do as much as you are able to do."  

كُنَّا إِذَا بَايَعْنَا رَسُولَ اللهِ ﷺ عَلَى السَّمْعِ وَالطَّاعَةِ يَقُولُ لَنَا فِيمَا اسْتَطَعْتَ