Praise be to Allah.
No doubt what has happened to your son is a trial for you, and we ask Allaah to grant you patience and make you steadfast in adhering to His religion; and we ask Him to heal your son. It is obvious that he has fallen prey to the effects of witchcraft so you should not blame him for the way in which he treats you. No rational person would be content to learn of any of the things that his wife has done and remain silent about them. But it seems that the witchcraft has affected him greatly, to such as extent that he agrees with her and has turned against you.
In the answer to question no. 11290 we have already explained that it is haraam to treat witchcraft by means of witchcraft. In that answer and in the answer to question no. 12918 we have explained the shar’i method of treating witchcraft.
You can treat your son by reciting Qur’aan over water and giving it to him to drink without his knowledge. And you have to constantly make du’aa’ whilst using this remedy, that Allaah may relieve him of this distress and harm.
Whether your son should be given his share of the inheritance depends on whether he will dispose of the money properly. If the money will fall into his hands or his wife’s hands and they will never dispose of it properly, then it is not permissible for you to let him have the money; you should keep it with you and spend on him and his children from it. This is a trust which has been given to you, and you should not be careless about it.
Allaah says (interpretation of the meaning):
“And give not unto the foolish your property which Allaah has made a means of support for you, but feed and clothe them therewith, and speak to them words of kindness and justice.
6. And try orphans (as regards their intelligence) until they reach the age of marriage; if then you find sound judgement in them, release their property to them, but consume it not wastefully and hastily fearing that they should grow up, and whoever (amongst guardians) is rich, he should take no wages, but if he is poor, let him have for himself what is just and reasonable (according to his labour). And when you release their property to them, take witness in their presence; and Allaah is All‑Sufficient in taking account”
[al-Nisa’ 4:5, 6]
Shaykh ‘Abd al-Rahmaan al-Sa’di said:
Sufaha’ [translated here as “the foolish”] is the plural of safeeh, which refers to one who is unable to dispose of money properly, either because he has no powers of reasoning, such as one who is insane or feeble-minded, etc, or because he is lacking in wisdom, such as a child and one who is immature. Allaah has forbidden guardians to give such people their wealth, for fear that they will destroy it and waste it, and because Allaah has made wealth means of support for His slaves, in their religious and worldly interests. These people will not look after it properly and guard it, so Allaah has commanded their guardians not to give it to them, rather they should provide for them from it, clothing them and spending on them from it, and taking care of their religious and worldly needs. And they should speak to them words of kindness and justice, by promising them, when they ask for it, that they will give it to them after they become mature and so on. They should speak to them kindly to soften their hearts. The fact that Allaah gives control of the wealth to the guardians indicates that they are obliged to take care of the wealth of the foolish just as well as they would take care of their own wealth, guarding it, disposing of it properly and not exposing it to danger.
This verse indicates that the cost of spending on the insane, the young and the foolish should come from their own wealth, if they have wealth, because Allaah says (interpretation of the meaning): “but feed and clothe them therewith” (v. 5).
This matter should be referred to the shar’i court and proof should be established that this son cannot handle his money properly, so that the court will prevent him from accessing it and will appoint a guardian to look after his money.
And Allaah knows best.