Before his death, my father-in-law verbally told his wife to distribute all his property, whether it be land or other things, in equal parts among his two sons, one daughter, and wife. Fearing this instruction, his two sons wasted a lot of the money during his lifetime. What is my mother-in-law to do now? The property has already been sold, and my mother-in-law gave an equal amount of money to her sons, and they almost finished all of the money, so what can my mother-in-law do now? Does Islam permit what has been mentioned?
All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
The will of your father in-law to divide his estate equally is a will that is of no effect because it contradicts the commandment of Allah about inheritance as Allah commended that the share of the male is twice that of the female and that the wife gets one eighth of the inheritance as long as the deceased [the husband] left behind direct heirs (children). There is no doubt that the commandment of Allah, The Wise, is more deserving of being executed than the will of a person. What you mentioned, that his sons waste and squander money, does not allow preventing them from receiving their full shares. Dividing the inheritance equally means reducing their shares.
If an heir is foolish, this requires that he be placed under Hajr (legal interdiction), but it does not permit depriving him of his share in the inheritance or part of it. Also, it is the Muslim judge who issues such Hajr.
The Fiqh Encyclopedia reads, “Restraining a foolish person from disposing of his wealth through the ruling of the judge: The majority of the scholars of Fiqh who are in favor of restraining the foolish person from disposing of his wealth are of the view that Hajr must be through the ruling of the judge, and they see that cancelling this Hajr must also be through the ruling of the judge… ”
What your mother-in-law is obliged to do now is to give the sons their legitimate share and divide the inheritance according to the Commandment of Allah. If she had already divided it in a way that is contrary to the Sharia, then she is obliged to take from her share and her daughter’s share what exceeded their rights and give her sons whatever was deducted from their shares.
Allah knows best.