"How to pray for Shia Muslims during Ashura ...Sunni and Shia Muslims observe Ashura for different reasons"

"Sunni and Shia Muslims observe Ashura for different reasons and in different ways. For some, Ashura is the day Noah exited the Ark and the Israelites escaped Egypt. For the minority Shia branch of Islam, which makes up 10 percent of Muslims worldwide , Ashura mourns the martyrdom of Mohammed's grandson Husayn ibn Ali, the third Shia Imam..."

https://www.mnnonline.org/news/how-to-pray-for-shia-muslims-during-ashura/