When we study history, we come to know that the Jews organized their traditions around their own calendar. The Jews had their own months which did not coincide with the Islamic calendar. There is no logic in saying that they ‘fasted on the 10th of Muharram’, unless it could be proven that this date always coincided with the Jewish day of fast. Their fasting did not take place every year on the day of ‘Ashura and certainly not in the holy month of Muharram.
Apparently, the tradition of the Jews at the time of the Holy Prophet (S) was that on the 10th of the month of Tishri of the Jewish calendar, Yom Kippur, the Jews observed a fast. They say God delivered Moses and his people and drowned Pharaoh and his forces on that day. It cannot be said, however, that Pharaoh was drowned on the day of ‘Ashura.
On the contrary, these events are said to have taken place on the 10th of Tishri which does not correspond to the day of ‘Ashura. Therefore, that which has been said about the fast of ‘Ashura having its roots in Judaism and that it has been imported from the Jews is baseless and not founded on truth.
Abu Rayhan says, “Tishri lasts thirty days… and on the tenth day of that month, the Jews start their fast of Yom Kippur, which some call ‘Ashura. This fast carries more virtues for the Jews than the other fasts. That is why it is wajib.”12
Hasan ibn ‘Ali Saqqaf Shafi‘i says, “We do not find any evidence to prove that the Jews used to fast or hold a festival on the tenth of Muharram. There is no written historical evidence to suggest this. On the contrary, they used to fast on the tenth of Tishri.”13
He also says, “The Jews have their own special calendar which has very apparent differences with the Islamic calendar. This calendar begins with the month of Tishri, which is followed by the month of Heshvan, and ends with the twelfth month called Elul…
The number of days in a normal year is either 353 or 354 or 355 days. However, in a leap year, the number of days is either 383 or 384 or 385. And therefore, the calendar that is now observed by the Jews is such that the months are lunar but the years are solar.”14
About the Arab calendar that was used before the Islamic calendar came into effect, Mahmud Pasha Falaki says, “It can be gathered and deduced from history that the Arab Jews also had ‘Ashura, but their ‘Ashura was on the tenth of Tishri which is the first month of their calendar according to Jewish civil law and the eighteenth month of their religious calendar. Also, the Jews follow a solar calendar.
Therefore, the day of ‘Ashura on which Pharaoh was drowned is not at all connected to Muharram. In addition to that, it was merely accidental that it coincided with the Holy Prophet’s (S) entry into Medina.”15
12. Al-Athar al-Baqiyah, p. 277.
13. Al-Hadi Magazine, no. 2, p. 37.
14. Ibid., p. 36.
15. Bustani, Da’irah al-Ma‘arif, vol. 11, p. 446.
Adapted from: "The Uprising of Ashura and Responses to Doubts" by: "‘Ali Asghar Ridwani"