The Prophet ﷺ said, "Fasting on the day of Arafah atones for the year before it and the year after it, and fasting on the day of Ashura atones for one year."Abdullah said, "My father said, 'Sufyan did not trace it back to the Prophet when he narrated it to us, though it does go back to him.'"
حدثنا عبد الله حدثنا نصر بن علي حدثنا سفيان فقال عن النبي ﷺ
Its chain of transmission is sahih, and it elevates the report that preceded it.