ANSWER:

This is not mandatory but highly recommended. 

You can fast only 10th as well.

QUESTION: Is it mandatory to fast 9th and 10th of the muharram ? Or i can only fast on the 10th of muharram

Fasting | July 27, 2023 12:58 am
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QUESTION: Sheikh, I really wanted to fast on the Day of Arafah this year, as I learnt about the Hadith that it expiates the sins of the previous and the upcoming years, but I got my periods, which was decreed for me by Allah. Will I get the reward, will my sins be forgiven (if I verbally seek Istaghfaar) while I cannot fast?
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QUESTION: Fasting the day of arafah expiates sins next year and previous year. If I fast on the day of Arafah, my minor sins next year will be expiated; does that mean that its okay for me to commit minor sins next year?