Abdullah bin Umar reported,

A man asked the Messenger of Allah ﷺ about the night prayer. The Messenger of Allah ﷺ replied, "The night prayer is offered in pairs of two. When one of you fears the approach of dawn, let him pray a single rakah, which will make all that he has prayed odd-numbered."

Muslim 1748

Sahih

و حدثنا يحيى بن يحيى قال قرأت على مالك عن نافع وعبد الله بن دينار

عن ابن عمر

أن رجلا سأل رسول الله ﷺ عن صلاة الليل فقال رسول الله ﷺ صلاة الليل مثنى مثنى فإذا خشي أحدكم الصبح صلى ركعة واحدة توتر له ما قد صلى

مسلم 1748صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Travelers' prayer and its shortening
Chapter
Night prayer is two rakats at a time and Witr is one rakat at the end of the night
Numbering
Darussalam 1748
Muslim 1748