The Authenticity of the Hadith Prohibiting Fasting on Saturday

Question:
The questioner says: What is the authenticity of the hadith, “Do not fast on Saturday except for what is obligatory upon you”? What is your view regarding those who say that it is not permissible to fast on Saturday, even if it is one of the white days, or even if it coincides with the Day of 'Arafah, and so on?

Answer:
What I know is that the prohibition of fasting on Saturday is not established from the Messenger of Allah (peace and blessings be upon him). However, it is disliked to single out Saturday for fasting. Singling it out means fasting on that day alone. But if one fasts on Saturday in conjunction with other days, such as the white days, where Saturday becomes one of them, there is no harm in that. Or if it coincides with the Day of 'Arafah and one fasts for the sake of the Day of 'Arafah, there is no harm in that. It is only when one singles it out because it is Saturday that it becomes disliked according to the scholars, because it involves imitating the Jews, as Saturday is the day the Jews hold in high esteem. Fasting on it involves imitating them. If the hadith were established, the prohibition would also apply, as it came from the Messenger of Allah (peace and blessings be upon him). In any case, fasting on Saturday is disliked as a disliked act of avoidance (makruh tanzihi), not as a forbidden act (makruh tahrimi). It is disliked to fast on it alone, but if it is fasted in conjunction with other days, such as coinciding with the white days or the Day of 'Arafah, or if a person is fasting and Saturday falls within that period, there is no harm in that.