The ruling on fasting on Friday alone

Question:
Is it permissible to fast on Friday?

Answer:
It is not permissible to single it out for fasting. The Messenger of Allah (peace and blessings be upon him) forbade this; he forbade singling it out for fasting. However, if a person is fasting and he fasts on Saturday with it, or fasts on Thursday with it, there is nothing wrong with that. Or if his fasting is making up missed days of Ramadan, or if it is a voluntary fast, there is nothing wrong with that. Or if he fasts it because it is the Day of 'Arafah, not for the sake of singling it out, but rather it coincided with the Day of 'Arafah so he fasted, or because he had missed days to make up and it was not possible for him to make them up except on Friday, not for the sake of Friday itself, but because it was not possible for him to make them up except on that day, then he is excused.