Ibn 'Umar (May Allah be pleased with them) reported:
The Prophet ﷺ said, "Salat during the night should consist of pairs of but if you fear that morning is near, then pray one Rak'ah as Witr."

[Al-Bukhari and Muslim].

وعن ابن عمر رضي الله عنهما، أن النبي ﷺ ، قال: "صلاة الليل مثنى مثنى، فإذا خفت الصبح فأوتر بواحدة". ((متفق عليه)) .