A man asked the Messenger of Allah ﷺ about prayer at night and the Messenger of Allah ﷺ said: "Prayer at night is two by two, then if one of you fears that dawn will break, pray one rak'ah to make the total number that he prayed odd."
أَنَّ رَجُلاً سَأَلَ رَسُولَ اللَّهِ ﷺ عَنْ صَلاَةِ اللَّيْلِ فَقَالَ رَسُولُ اللَّهِ ﷺ صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا خَشِيَ أَحَدُكُمُ الصُّبْحَ صَلَّى رَكْعَةً وَاحِدَةً تُوتِرُ لَهُ مَا قَدْ صَلَّى