Answer
Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
If you couldn’t pray sunnah before Fajr in congregation, then you should make it up after before sunrise. If, however, you forgot to make it up before sunrise you can do so twenty minutes after sunrise.
In responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
If you couldn’t pray sunnah before Fajr in congregation, then you should make it up after before sunrise. If, however, you forgot to make it up before sunrise you can do so twenty minutes after sunrise.
The Prophet Muhammad (peace be upon him) said, “Whoever misses the two rakahs before Fajr, let him offer it after sunrise.” (At-Tirmidhi)
We read in another report from Umm Salamah that she saw the Prophet that he made up for the two rakahs of Sunnah after Zhuhr after the Asr prayer as he missed it because of being preoccupied with the delegation of Bani Abd al-Qays (Al-Bukhari and Muslim)
Another tradition from Aishah says: if the Prophet ever missed the four rakahs after Zhuhr he would make up for them later.” (At-Tirmidhi)
? Read Also: What Is the Time for Fajr Prayer?
We read in another report from Abu Said al-Khudhri that the Prophet said, “Whoever oversleeps and forgets to pray Witr, he should pray it when he wakes up or remembers.” (At-Tirmidhi and Abu Dawud)
Almighty Allah knows best.
Source: https://askthescholar.com/