The preference and tradition of fast on Ashura has been constantly considered and emphasized by Sunnites. In one hand, this day is of great importance to Shiites and to them fasting in this day is considered as innovation and disapproved issue not a traditional and preferred one. According to the historical investigations, fasting on Ashura has not been in Muharram but on the 10th day of Tishri month being concurrent with the fasting of Jewish in the name of “kipur” or “Asur”. The reason of making mistake about this day and the 10th day of Muharram has to do with the similarity of pronunciation by Arabs who pronounce both days as Ashura. On the other hand, fasting on that day has been abrogated through the necessity of the fast in Ramadan. The renovation of this abrogated decree is not considered as tradition but an innovation being propagated by people in line with Umayyad policies. In this regard, the scientific statement of this issue can be effectual in lessening the sectional and religious challenges. Considering the jurisprudential Points of view and narrations of this event in the sources of the two sects and through a historical approach, this writing is to answer the question concerning the origin of fasting on Ashura of early Islam and its decree in Prophetic time.
)