تاريخ الطبري
In the Islamic year 6 AH (627 – 628 CE), Muhammad is said to have had letters written to the great rulers of the Middle East, proclaiming the continuation of the monotheistic faith with its final messages and inviting the rulers to join. The purported texts of some of the letters are found in Muhammad ibn Jarir al-Tabari's "History of the Prophets and Kings". Tabari writes that a deputation was sent to an Egyptian governor named as "al-Muqawqis".