Narrated `Abdullah bin Dinar:
`Abdullah Bin `Umar wrote to `Abdul 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.'
Reference: Sahih al-Bukhari 7272
In-book reference: Book 96, Hadith 5
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 9, Book 92, Hadith 377