Fasting On The Day Of Ashura

Ibn ‘Abbas رضي الله عنه relates that

the Messenger of Allah صلى الله عليه وآله وسلم fasted the the day of ‘Ashura’ and strongly recommended fasting it. 

[Al-Bukhari and Muslim]

Abu Qatada رضي الله عنه  relates that the Messenger of Allah صلى الله عليه وآله وسلم was once asked about fasting the day of ‘Ashura’, and he answered,

“It atones for the misdeeds of the past year.”

[Muslim]