You might be wondering what the big deal is all about with fasting tomorrow (Tuesday 11th October). Well here it is
Ibn Abbas RadhyAllahu ‘anh reports:
‘When the Prophet ﷺ arrived in Madinah, he observed the Jews fasting on the day of ‘Ashurah, so the Prophet ﷺ asked them,
“Why do you fast on this day?”
They replied, “This is a great day. It is on this day that Allah saved Musa and his followers while drowning Pharoah and his people, so Musa fasted this day out of gratitude to Allah. That is why we fast on this day.”
The Prophet ﷺ replied, “We have more right to Musa than you (i.e. we love Musa and follow what he came with [Islam] more than you do),” and thereupon the Prophet ﷺ fasted this day and commanded the people to do likewise.’
[Sahih al Bukhari]
A man asked the Prophet ﷺ about the virtues of fasting the day of ‘Ashurah.
He ﷺ said,
‘I hope that Allah will make it a cause to expiate the sins of the previous year.’
It is advisable to also fast the day preceding or the day following ‘Ashurah. One should fast two days: 9th and 10th of Muharram or the 10th and 11th.
The Prophet ﷺ said:
‘If I live until next year, I will fast the 9th along with the 10th (of Muharram).’
This was so that his fasting would differ from that of the Jews.