When is Fasting Prohibited?

While fasting is generally encouraged, there are times in which fasting is disliked or even prohibited. The days of 'Eid are one of those prohibited days. Fasting on the first day of Eid al-Fitr and the four days of 'Eid al-Adha is haram. Because these days are celebrated by all Muslims, they come together and have feasts and treats altogether. It would not appreciated a person to fast on such a day. Fasting is prohibited for women during their haydh (menstruation) and nifas (lochia) periods, and for the ones who could end up in a vital situation if they fast. Similarly, 

 it is prohibited to fast subsequent days without iftar(sawm al-wisal). It is makruh to single out a fast on Friday, Saturday, or the days of Ashura, Nawruz and Mehregan (a Zoroastrian festival).. Friday is considered a day of joy by the Muslims, so it is makruh to fast on the this day. (İbrahim Kâfi Dönmez, “Oruç”, DİA, XXXIII, 416-425, İlmihal, 402-403))