Sunan an-Nasa'i · Hadith 1693
The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day - كتاب قيام الليل وتطوع النهار
أخبرنا قتيبة، قال حدثنا خالد بن زياد، عن نافع، عن ابن عمر، قال قال رسول الله صلى الله عليه وسلم " صلاة الليل مثنى مثنى والوتر ركعة واحدة " .
It was narrated that Ibn Umar said: "The Messenger of Allah (ﷺ) said: 'Prayer at night is two by two, and witr is one rak'ah.'"
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).