Hadith 5:45
She said that God’s messenger would be overtaken by the dawn in Ramadan when he was in a state of sexual defilement, not owing to a dream, and would wash and fast. (Bukhari and Muslim.)
وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُدْرِكُهُ الْفَجْرُ فِي رَمَضَانَ وَهُوَ جُنُبٌ مِنْ غَيْرِ حُلْمٍ فَيَغْتَسِلُ وَيَصُومُ
Original Reference: Mishkat al-Masabih 2001