What is the ruling on money acquired by the father through usury or forbidden workshops, for which he did not pay zakat, and does his ignorance of the ruling prohibiting these matters affect their permissibility, and is it permissible for the son to take this money if the father refuses to dispose of it?

If the father was ignorant of the prohibition of what he was engaged in from unlawful earnings, then his repentance effaces what preceded it, and he is not required to dispose of what he earned. However, if he was aware of its prohibition, he must give out the amount of the unlawful earnings. If he does not know the exact amount, he should err on the side of caution and strive to estimate it.

If the father refuses to give out the unlawful earnings, the son is not permitted to take money from him without his permission. The son may benefit from his father's commingled lawful and unlawful wealth, except for what he knows to be from the very substance of the unlawful.

As for zakat, it is obligatory upon the father for all past years, and it is a debt that does not lapse with the passage of time. It is due on lawful wealth, whereas the entirety of the unlawful wealth must be given out.