What is haram in Dhul Hijjah?

Approved answer

Understanding Fasting in Dhul Hijjah

It is forbidden (haram) to observe a fast on the 10th of Dhul Hijjah, known as the day of Eid al-Adha. If you are unable to fast for all nine days of Dhul Hijjah, it is recommended that you at least fast on the 9th of Dhul Hijjah, which corresponds to the Day of Arafah.