Which day fasting is haram?

Days When Fasting is Prohibited

Fasting is not allowed on Eid al-Adha and the three subsequent days because, as reported by Abu Hurairah, Muhammad stated: "You are not to fast these days. They are days of eating, drinking, and remembering Allah." Additionally, fasting on Eid al-Fitr is also forbidden. Furthermore, it is not permissible to exclusively fast on Fridays.