'Aishah (May Allah be pleased with her) reported:
The Messenger of Allah (ﷺ) used to perform four Rak'ah of Duha prayer (at the forenoon) and would add to them whatever Allah wished.[Muslim]. (RU)
App reference (RU): Book 9, Hadith 151 (RU)
Arabic/English book reference (RU): Book 9, Hadith 1141 (RU)