"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»