Hazrat Ikrimah says that whether you recite (Qur'an) in the Sunnah of Fajr or not, if you do recite, then keep it brief, but definitely perform these two rak'ahs, even if you have to offer them on the way.

Hazrat Mujahid says that if you enter the mosque during the congregation and you have not performed the Sunnah of Fajr, then first perform these Sunnah, even if you fear missing the first rak'ah.

Hazrat Wabra says that I also saw Hazrat Ibn Umar (may Allah be pleased with them both) doing the same. Someone told me that Hazrat Ibn Umar (may Allah be pleased with them both) did this twice: once, when he came during the congregation, he performed the Sunnah prayers of Fajr in a corner of the mosque; then, the second time, he joined the congregation without having performed the Sunnah prayers of Fajr.

6576 - (And) (1) Someone who saw him narrated to me (2) that he did it twice: he came once (while they) (3) were in prayer (so he prayed them) (4) in the side of the mosque, then he entered another time and prayed with them and did not pray them (5).

Ibrahim has considered it disliked to perform the Sunnah prayers of Fajr in the mosque during the congregation. He states that these Sunnah prayers should be performed during the congregation at the corner or at the door of the mosque.

Hazrat Abu Darda says that sometimes I come to the mosque during the congregation of the Fajr prayer; I offer the two Sunnah (units) and then join the congregation.

Hazrat Ibn Sirin says that if a person enters the mosque during the congregation of Fajr, he should join the congregation and not offer the two Sunnah. Because the obligatory prayer that he would miss is of a higher status than the Sunnah.

Ibn Aun reports that I asked Ibrahim about this matter, and he replied that the missed obligatory prayers are to be made up, whereas missed voluntary prayers are not to be made up.

Hazrat Ibn Sirin says that the prayer missed with the Imam is better than these two rak‘ahs.

Hazrat Hammad says that do not enter the mosque without performing the two Sunnah of Fajr, even if you have to perform them on a heap of garbage.