Jami` at-Tirmidhi 752
جامع الترمذي#752SahihAbu Qatadah narrated that :the Prophet said: "Fast the Day of Ashura, for indeed I anticipate that Allah will forgive (the sins of) the year before it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 8:71