What is the ruling on fasting on the tenth day of Muharram?
It is not forbidden to fast on the tenth of Muharram; however, it is better to abstain from eating and drinking until after Asr Prayers as a sign of mourning for Imam Hussain. Then, at that time (i.e. after Asr), drinking a little bit of water since the children and women of Ahl al-Bayt were able to drink water at that time on the tenth day of Muharram.