Sahih Bukhari Volume 9, Book 93, Hadith 7207

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.‏

Narrated By '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."