Maliks Muwatta Book 055, Hadith Number 003.

Section : About the Oath of Allegiance.

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."