Is it permissible to fast Saturday or Sunday?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

For singling out fasting on Saturday, please refer to Fatwa: 87220.

As regards fasting on Sunday, it is dislikeable to single out fasting this day. The evidence for this is what Um Salamah narrated that the Prophet used to fast most of the days on Saturday and Sunday, and he used to say: "These are the days of celebrations of the polytheists, and I like to be different from them." [Ibn Khuzaymah] So this is an evidence that if one fasts either day he should fast one day before or after fasting on Saturday or Sunday. But if it coincides with a day that usually one fasts, then there is nothing dislikeable in that. However, the Shaafi'ee and Hanafi schools are of the view that it is dislikeable to fast this day. The Hanbali school is of the view that it is dislikeable to fast any day that is celebrated by the Jews or Christians or any day they single out for glorification, excepts if this day coincides with a day that one usually fasts. The evidence of the majority of the scholars in interpreting the forbiddance of fasting this day by being dislikeable, is the fasting of our Prophet Daawood that he used to fast every other day. They said: "This is an evidence that whoever fasts every other day, he will be obliged to fast Saturday or Sunday." This statement is a strong deduction and is of great consideration. The same ruling applies also on singling out fasting on Friday.

Allaah knows best.