Musannaf Ibn Abi Shaybah

Hazrat Qais bin Amr narrates that the Noble Prophet (peace and blessings be upon him) saw a man performing two rak'ahs after the morning prayer. The Prophet (peace and blessings be upon him) said: "Are you performing the morning prayer twice?" The man replied, "I was unable to perform the two Sunnah before the Fajr prayer, so I have just performed them now." The Prophet (peace and blessings be upon him) remained silent.

Hazrat Ata narrates that a man performed the morning prayer with the Prophet Muhammad (peace and blessings be upon him). When the Prophet (peace and blessings be upon him) finished the prayer, that man stood up and performed two rak‘ahs. The Prophet (peace and blessings be upon him) asked him: "What are these two rak‘ahs?" He replied: "O Messenger of Allah (peace and blessings be upon him)! I came (to the mosque) when you were already in prayer, and I had not yet performed the two rak‘ahs before Fajr. I disliked that you were leading the prayer and I should perform those two rak‘ahs. So when you completed the prayer, I performed those two rak‘ahs." The narrator says: The Prophet (peace and blessings be upon him) neither ordered him nor forbade him (from this).

Masma’ bin Thabit narrates that I saw Hazrat Ata’ doing the same.

It is narrated about Hazrat Sha'bi that when he missed the two rak'ahs (Sunnah) of Fajr, he would perform them after the Fajr (obligatory) prayer.

Yahya bin Kathir says that I heard Qasim say: If I have not performed these two rak‘ahs until I have offered the Fajr (obligatory prayer), then I perform them after the sunrise.

It is narrated about Hazrat Ibn Umar (may Allah be pleased with them both) that he performed the two rak'ahs (Sunnah) of Fajr after Ishraq. And (Imam) Abu Hanifa's opinion has been mentioned that: A person is not required to make up (qada) for them (the Sunnah of Fajr).