Sunan Abi Dawud 2442
سنن أبي داود#2442SahihAishah said:The Quraish used to fast on the day of 'Ashurah in pre Islamic days. The Messenger of Allah (ﷺ) would fast on it in pre-Islamic period. When the Messenger of Allah (ﷺ) came to Medina, he fasted on it and commanded to fast on it. When the fast of Ramadan was prescribed, that became obligatory, and (fasting on) 'Ashurah was abandoned. He who wishes may fast on it and he who wishes may leave it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Bukhari (2002) Sahih Muslim (1125)
In-book reference: 14:130