Urwah narrates from Sayyidah Aishah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) used to pray eleven rak'ahs at night, making one of them witr. When he (peace and blessings be upon him) finished, he would lie down on his right side. When the mu'adhdhin came, he (peace and blessings be upon him) would pray two light rak'ahs.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4774