Abu Hurairah (May Allah be pleased with him) reported:
My Khalil (the Messenger of Allah (ﷺ)) directed me to fast three days of each month, and to observe two Rak'ah Duha (optional prayer) at forenoon, and to perform the Witr prayer before going to bed.[Al- Bukhari and Muslim].
App reference: Book 9, Hadith 149
Arabic/English book reference: Book 9, Hadith 1139