When the Prophet Muhammad arrived in Medina, he reported that the Jews of Medina were fasting and celebrating this day in memory of Moses’s victory over the Egyptian Pharaoh. He called on Muslims to also fast on that day and the day before it, because Moses is considered to be a prophet of Islam. The Day of Ashura is also deemed to be the day Noah’s Ark reached land, and also the day that Abraham was spared from fire.
Ashura is particularly important to the Shia people. It is a day of mourning to commemorate the day the Prophet Muhammad’s grandchild Husain was martyred.