Sunan Ibn Majah
1731
Daif+2

It was narrated that Qatadah bin Nu’man said:“I heard the Messenger of Allah (ﷺ) say: ‘Whoever fasts the Day of ‘Arafah, his sins of the previous and following year will be forgiven.’”

DaifAl-Albani
Sahih LighairihiMuhammad Fouad Abd al-Baqi