Hadithcore
Riyad as-Salihin, 1169

Ibn 'Umar (May Allah be pleased with them) reported:

The Prophet (ﷺ) performed the night prayer in pairs (i.e., Rak'ah) and made it odd number by observing one Rak'ah (as Witr). <b>[Al-Bukhari and Muslim]</b>.

وعنه قال‏:‏ كان النبي صلى الله عليه وسلم ، يصلي من الليل مثنى مثنى، ويوتر بركعة‏.‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏ ‏.‏

References1 variant
In-Book Reference
Book 8, Hadith 179
Sharh · explanationclick to expand
<b>Guidance from the Hadiths:</b><br> 1) The Prophet’s guidance regarding Qiyām al-Layl is to pray two Rak‘ahs by two Rak‘ahs.<br> 2) When dawn breaks, the time of Witr ends, and the minimum for Witr is one Rak‘ah.