" صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا خِفْتَ الصُّبْحَ فَأَوْتِرْ بِوَاحِدَةٍ "
It was narrated from Salim, from his father, that : The Prophet (ﷺ) said: "Prayers at night are two by two, then if you fear that dawn will come, pray witr with one rak'ah."