Sahih al-Bukhari 7205
Narrated `Abdullah bin Dinar:
When the people took the oath of allegiance to `Abdul Malik, `Abdullah bin `Umar wrote to him: "To 
Allah's Slave, `Abdul Malik, Chief of the believers, I give the Pledge of allegiance that I will listen to 
and obey Allah's Slave, `Abdul Malik, Chief of the believers, according to Allah's Laws and the 
Traditions of His Apostle in whatever is within my ability; and my sons too, give the same pledge."
حَدَّثَنَا عَمْرُو بْنُ عَلِيٍّ، حَدَّثَنَا يَحْيَى، عَنْ سُفْيَانَ، قَالَ حَدَّثَنِي عَبْدُ اللَّهِ بْنُ دِينَارٍ، قَالَ لَمَّا بَايَعَ النَّاسُ عَبْدَ الْمَلِكِ كَتَبَ إِلَيْهِ عَبْدُ اللَّهِ بْنُ عُمَرَ إِلَى عَبْدِ اللَّهِ عَبْدِ الْمَلِكِ أَمِيرِ الْمُؤْمِنِينَ إِنِّي أُقِرُّ بِالسَّمْعِ وَالطَّاعَةِ لِعَبْدِ اللَّهِ عَبْدِ الْمَلِكِ أَمِيرِ الْمُؤْمِنِينَ، عَلَى سُنَّةِ اللَّهِ وَسُنَّةِ رَسُولِهِ، فِيمَا اسْتَطَعْتُ، وَإِنَّ بَنِيَّ قَدْ أَقَرُّوا بِذَلِكَ‏.‏