Muharram · a Light

He found a fast in Madinah and joined it

Ibn Abbas reported that when the Prophet ﷺ arrived in Madinah he found the Jewish community fasting on the day of Ashura. He asked what the day was. They told him it was the day Allah saved Moses and his people from Pharaoh, so Moses fasted it. He said that the Muslims had a closer claim to Moses, and he fasted the day and told them to fast it. Quraysh had also marked the tenth of Muharram before Islam. What is being described is not the invention of a fast but the adoption of one, with an explanation of why an older prophet's rescue belongs to a newer community as well.

Ibn Abbas · Madinah, first year

Source · Bukhari 2004, Muslim 1130