Sunan an-Nasai 16413
In-book no 1677أَخْبَرَنَا أَحْمَدُ بْنُ مُحَمَّدِ بْنِ الْمُغِيرَةِ، قَالَ حَدَّثَنَا عُثْمَانُ، عَنْ شُعَيْبٍ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنِ ابْنِ عُمَرَ، قَالَ سَأَلَ رَجُلٌ مِنَ الْمُسْلِمِينَ رَسُولَ اللَّهِ صلى الله عليه وسلم كَيْفَ صَلاَةُ اللَّيْلِ فَقَالَ " صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا خِفْتَ الصُّبْحَ فَأَوْتِرْ بِوَاحِدَةٍ " .
It was narrated that Ibn Umar said: "A man from among the Muslims asked the Messenger of Allah (ﷺ): 'How are prayers at night to be done?' He said: 'prayers at night are (offered) two by two, then if you fear that dawn will come, pray witr with one.'"