"The Messenger of Allah ﷺ set out at nightfall, then stopped to camp at the end of the night, and he did not wake up until the sun had risen or had partly risen. He did not pray until the sun had risen (fully), then he prayed, and that was the 'middle prayer' (Salat Al-Wusta)."
أَدْلَجَ رَسُولُ اللَّهِ ﷺ ثُمَّ عَرَّسَ فَلَمْ يَسْتَيْقِظْ حَتَّى طَلَعَتِ الشَّمْسُ أَوْ بَعْضُهَا فَلَمْ يُصَلِّ حَتَّى ارْتَفَعَتِ الشَّمْسُ فَصَلَّى وَهِيَ صَلاَةُ الْوُسْطَى
[Machine] Ibn Abbas said, "Verily, the Fajr prayer is from the time of dawn until the rising of the sun's ray. Its time passes and the Messenger of Allah ﷺ used to delay it until some of the sun rises or part of it rises. He would not wake up until the sun had risen and he would not pray until it had risen, and that is the middle prayer."
قَالَ ابْنُ عَبَّاسٍ «إِنَّ صَلَاةَ الْفَجْرِ مَا بَيْنَ طُلُوعِ الْفَجْرِ إِلَى طُلُوعِ شُعَاعِ الشَّمْسِ وَيَذْهَبُ وَقْتُهَا وَقَدْ أَدْلَجَ رَسُولُ اللهِ ﷺ ثُمَّ عَرَّسَ فَلَمْ يَسْتَيْقِظْ حَتَّى طَلَعَتِ الشَّمْسُ أَوْ بَعْضُهَا فَلَمْ يُصَلِّ حَتَّى ارْتَفَعَتْ فَصَلَّى وَهِيَ صَلَاةُ الْوُسْطَى»
"The Messenger of Allah ﷺ set out at nightfall, then stopped to camp at the end of the night, and he did not wake up until the sun had risen or had partly risen. He did not pray until the sun had risen (fully), then he prayed, and that was the 'middle prayer' (Salat Al-Wusta)." (Using translation from Nasāʾī 625)
«أَدْلَجَ رَسُولُ اللهِ ﷺ ثُمَّ عَرَّسَ فَلَمْ يَسْتَيْقِظْ حَتَّى طَلَعَتِ الشَّمْسُ أَوْ بَعْضُهَا فَلَمْ يُصَلِّ حَتَّى ارْتَفَعَتِ الشَّمْسُ فَصَلَّى وَهِيَ صَلَاةُ الْوُسْطَى»