Sunan an-Nasai 16432
In-book no 1696أَخْبَرَنَا الْحَسَنُ بْنُ مُحَمَّدٍ، عَنْ عَفَّانَ، قَالَ حَدَّثَنَا هَمَّامٌ، قَالَ حَدَّثَنَا قَتَادَةُ، عَنْ عَبْدِ اللَّهِ بْنِ شَقِيقٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَجُلاً، مِنْ أَهْلِ الْبَادِيَةِ سَأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم عَنْ صَلاَةِ اللَّيْلِ قَالَ " مَثْنَى مَثْنَى وَالْوَتْرُ رَكْعَةٌ مِنْ آخِرِ اللَّيْلِ " .
It was narrated from Ibn 'Umar that: A man from among the people of the desert asked the Messenger of Allah (ﷺ) about prayer at night. He said:"(It is) two by two, and Witr is one rak'ah at the end of the night."