The Prophet ﷺ used to pray eleven rakats during the night, making one of them the witr, then he would lie down on his right side.
أخبرنا إسحق بن منصور قال أنبأنا عبد الرحمن قال حدثنا مالك عن الزهري عن عروة
أن النبي ﷺ كان يصلي من الليل إحدى عشرة ركعة يوتر منها بواحدة ثم يضطجع على شقه الأيمن
Muslim narrated it in the Book of the Prayer of the Traveler, chapter on the night prayer and the number of units the Prophet ﷺ prayed at night, etc., hadith no. 736, from the hadith of Malik with this chain, and it is also found in Muwatta (Yahya), 1/120, and in Kubra, hadith no. 445.Bukhari also narrated it in the Book of Witr, chapter on what has been said about Witr, hadith no. 994, from the hadith of Zuhri with this chain, with the wording, "And he would pray two units before the Fajr prayer, then lie down on his right side until the muezzin came to him for the prayer."Both wordings are sahih and preserved.