Does the exploitation by the mother and her unmarried daughter of their deceased father's building—after the consent of the rest of the children—and taking its monthly rent to spend on themselves, constitute consuming ill-gotten wealth, and what is the ruling of the Sharia on that?

Upon the death of the inheritor, their wealth transfers directly to the heirs. The division of inheritance may not be delayed unless all heirs consent. If they agree not to divide it, there is no harm. However, if any one of them desires their share, it must be given to them. Renouncing an inheritance is valid if the renunciant is an adult, of sound mind, and not coerced; they are not entitled to retract their renunciation thereafter.

In this case, the sons' relinquishment of their right to the property is a forbearance from demanding division, and their right to the property remains preserved for them. Should any of them demand their right, they are entitled to receive it. The rent you receive from the second floor is permissible with the permission and consent of your children. Wealthy children are obligated to spend on needy parents and poor brothers and sisters.

As for the son who demands his right, he should be given his share either from the house's rent or its sale price. He must know that he has wronged his mother and sister, and he is obligated to provide for them if they are needy. His brothers should advise him.