The mother of al-Hasan narrates from Umm Salamah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) used to pray two rak'ahs sitting after the witr.
This Maymun is from Basra and there is no harm in him, except that he used to commit tadlis (concealing a narrator); Imam Ahmad bin Hanbal (may Allah have mercy on him) and others said this. It has also been reported via Zakariyya bin Hakim from al-Hasan, and Hisham differed from both of them, narrating it from al-Hasan from Sa'd bin Hisham from Aishah (may Allah be pleased with her). Imam al-Bukhari (may Allah have mercy on him) said: This is more correct.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4822