Ibn 'Abbas (May Allah be pleased with them) reported:
The Messenger of Allah (ﷺ) said, "If I remain alive till the next year, I shall also observe fast on the ninth of Muharram."[Muslim]. (JA)
App reference (JA): Book 9, Hadith 263 (JA)
Arabic/English book reference (JA): Book 9, Hadith 1253 (JA)