Abdullah bin Umar reported,

A man came to the Prophet ﷺ while he was delivering a sermon and asked, "How is the night prayer performed?"He replied, "Two units at a time. When you fear that dawn is approaching, pray a single unit as witr, which will make all that you have prayed odd-numbered."Walid bin Kathir said, Ubaydullah bin Abdullah told me that Ibn Umar narrated to them that a man called out to the Prophet ﷺ while he was in the mosque.

Bukhari 473

Sahih

حدثنا أبو النعمان قال حدثنا حماد بن زيد عن أيوب عن نافع

عن ابن عمر

أن رجلا جاء إلى النبي ﷺ وهو يخطب فقال كيف صلاة الليل فقال مثنى مثنى فإذا خشيت الصبح فأوتر بواحدة توتر لك ما قد صليت قال الوليد بن كثير حدثني عبيد الله بن عبد الله أن ابن عمر حدثهم أن رجلا نادى النبي ﷺ وهو في المسجد

البخاري 473صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Prayer
Chapter
Shaving and sitting in the masjid
Numbering
Darussalam 473
Bukhari 473