Amina Inloes, Amina Inloes is originally from the US and has a PhD in Islamic Studies from the University of Exeter on Shi'a hadith. She is the program leader for the MA Islamic Studies program at the... Answered 11 months ago

Sh'is do not accept the hadith saying to fast on Ashura as valid. They are considered fabrications which came about in/after the time of Yazid to promote Ashura as a day of celebration. (Indeed, in some areas, Ashura is still celebrated as a holiday.)

For more information, you can look at resources such as this: https://www.al-islam.org/understanding-karbala-allamah-sayyid-saeed-akhtar-rizvi/appendix-4-fasting-ashura