Is it permissible to fast on the 25th of December, which coincides with Christmas Day?

It is disliked to fast on a day of the disbelievers' holidays unless it coincides with a customary fast, such as fasting on Mondays or Thursdays. It is also disliked to fast on Saturday alone because it is an imitation of the Jews. Similarly, fasting on Nowruz and Mehragan is disliked as it is an imitation of the Zoroastrians. It is disliked to single out any holiday of the disbelievers for fasting, or any day they single out for veneration, unless it coincides with a customary fast, in which case there is no dislike.