What is the ruling on the cooperative housing in which the father bought a house in 2002, claiming that the state gave him a grant and he pays the remainder in installments, and that it is not a usurious loan from the bank? Is the father sinful if there was usury that he did not realize? Is it permissible for the son to live in this house?

The state's bearing of the usurious interest does not permit entering into a usurious contract. However, if the father entered into the transaction unknowingly of its prohibition, then it is hoped that there will be no sin upon him, due to Allah's saying: (And there is no blame upon you for that in which you have erred, but [only for] what your hearts intended) and the Prophet's (peace be upon him) saying: "Indeed, Allah has forgiven my nation for [their] mistakes and forgetfulness." There is no harm in benefiting from the dwelling, because the prohibition of a usurious loan pertains to the liability of the one who takes it, not to the object consumed therein.