I heard the Messenger of Allah ﷺ on the pulpit being asked about the night prayer. He said, "Two by two, and when you fear the approach of dawn, pray a single rakah as witr."
أخبرنا محمد بن منصور قال حدثنا سفيان عن ابن أبي لبيد عن أبي سلمة
سمعت رسول الله ﷺ على المنبر يسأل عن صلاة الليل فقال مثنى مثنى فإذا خفت الصبح فأوتر بركعة
[Sahih] Reported by Ibn Majah in Iqamat al-Salawat, Chapter on what has been said about the night prayer being two units, hadith no. 1320, from the narration of Sufyan bin Uyayna, with this chain, and the hadith has very many corroborating witnesses.