Fasting on the day of `Eed

Question: What is the ruling on someone who fasts on the Day of ‘Eed despite knowing that it is the Day of ‘Eed?

Answer: It is not permissible to fast on the Day of ‘Eed based on the Saheeh (authentic) Hadeeths reported from the Prophet (peace be upon him) that forbid observing Sawm (Fast) on the days of ‘Eed-ul-Fitr (the Festival of Breaking the Fast) and ‘Eed-ul-Ad-haa (the Festival of the Sacrifice). Muslim scholars have agreed by Ijma‘ (consensus) on the prohibition of this. Anyone who does this should make Tawbah (repentance to Allaah) and resolve never to do it again… read more here.