What is the ruling on fasting on Saturday if it coincides with a customary fast?

The questioner : The question that follows is the issue of the prohibition of fasting on Saturday absolutely, even if one fasted days before and Saturday falls during the fast. Does he have to break his fast on that day because of the hadith of prohibition? Is the prohibition specific to Saturday itself, or is it for a cause?

The Shaykh : I think you were present at the session, weren't you?

The questioner : Hello. No change.

The Shaykh : Yes. For this reason. Do you remember the hadith that was mentioned in it?

The questioner, until you find.

The Shaykh : Is it absolute or restricted?

The questioner : In the middle, and I know. Huh? In the middle, and I know. That's it.

The Shaykh : How do you not know?

The questioner : No, it is not obligatory upon him.

The Shaykh : If a person came to you as a guest and you said to your son, "Do not feed so-and-so except bread," is this absolute or restricted? Restricted. Restricted.
Correct, this is the Arabic language, and people know it by their style and their Arabic instinct. We have discussed this issue in some detail in a previous session, and we said that it is not permissible for us to say in such clear Arabic speech that we are correcting the Messenger, so we say . Otherwise, if one precedes it by a day or delays it by a day, this would be correcting the Lawgiver, correcting the Messenger (peace and blessings be upon him). This is absolutely not permissible. And what compels the Muslim to put himself, as it is said, into a rabbit hole in such interpretations? And what stops him at this type of interpretation and does not go beyond it to others? For example, the day of the festival comes, Monday. Is it permissible to fast it?
We would say, by consensus, both ancient and modern, no. Well, why do we not restrict this absolute prohibition? He prohibited fasting on the day of the festival except for the day before it or the day after it? The same response applies to this as applies to that. The one who accepts that and does not accept this has nothing at all except custom and blind following. And perhaps this amount is sufficient as an answer to this question, unless you still have a difficulty, in which case I am ready to hear it from you and answer it for you.