Fajr sunnah can be read when the congregation starts?

17 rakats of obligatory prayers at five times a day as well as 12 rakats of sunnah prayers are very meritorious. Allah’s Messenger (may peace be upon him) used to perform these prayers regularly. These are called Muaqqadah in the Sunnah. The Prophet (peace be upon him) said:

مَنْ صَلَّى اثْنَتَيْ عَشْرَةَ رَكْعَةً فِي يَوْمٍ وَلَيْلَةٍ بُنِيَ لَهُ بِهِنًّ بَيْتٌ فِي الْجَنَّةِ

Whoever prays twelve rakats every day and night, a house will be built for him in Paradise. (Sahih Muslim: 728)

In Sunan Tirmidhi’s narration, it is mentioned in detail when and how to perform the 12 rakat prayers. Nabiji (pbuh) said,

أَرْبَعًا قَبْلَ الذُّهْرِ وَرَكْعَتَيْنِ بَعْدَهَا وَرَكْعَتَيْنِ بَعْدَ المْغرب وَرَكْعَتَيْنِ بعد الْعشَاء وَرَكْعَتَيْنِ قبل صَلَة الفَجْرِ
Four rak’ats must be performed before Zohr, two rak’ats after Fajr, two rak’ats after Maghrib, two rak’ats after ‘Isha’ and two rak’ats before Fajr. (Sunan Tirmidhi: 415)

Among these twelve rakats, the special virtues and importance of the two rakats before Fajr have been described separately in various hadiths. In a hadith, Rasulullah Sallallahu Alaihi Wasallam said,

لا تدعوا ركعتي الفجر, ون تردتكم الخيل.

Even if the army pursues you, do not leave the Fajr Sunnah. (Musnad Ahmad: 9253)

For this reason, when the Fajr congregation starts and the Sunnah is recited, even if there is a fear of rushing the first rakat, the Fajr durakat Sunnah prayer should be offered and then the congregation should be joined. It has been narrated about some prominent Companions that they used to recite the Fajr Sunnah even after the Fajr Jamaat had started. Imam Tahabi (RA) mentioned in his book ‘Sharhu Ma’anil Asar’, Abu Darda (RA) entered the mosque at the time of Fajr and found people lined up in the Fajr congregation, but he would stand in a corner of the mosque and recite the Sunnah, then join the congregation. (Sharhu Maanil Asar: 1/256)

However, if there is a possibility that the second rakat of the congregation or the congregation will run away when the sunnah is recited, then the sunnah will not be recited; Rather, he will join the congregation and perform Durakat Namaz as Qaza after sunrise.