Fiqh-us-Sunnah Volume 002, Supererogatory Prayer, Fiqh 2.006.

Section : Supplication after finishing the two sunnah rak'at before the fajr prayer.

An-Nawawi says in al-Azhkar. "It is related in the book of Ibn as-Sanni from Abu al-Malih (whose name was 'Aamr ibn Usamah) on the authority of his father that his father had prayed the two rak'at of the dawn [before salatul fajr] and the Prophet sallallahu alehi wasallam was praying the two rak'at close to him, and he heard the Prophet say, while sitting:

'O Allah, Lord of Jibrail, Israfeel, Mikail, and Muhammad, the Prophet, I seek refuge in Thee from the Fire,'"...three times.

He also records from Anas that the Prophet said: "Whoever says, on Friday morning before the salatul fajr,

'I seek the forgiveness of Allah, there is no other god except Him, the Living, the Sustaining, and I repent unto him,' three times, Allah will forgive his sins even if they were as abundant as the foam on the sea."