Is money earned from working in a factory, part of whose construction was financed by a usurious loan, lawful? Am I held religiously accountable for this loan, and what should I do in this situation?

Usury (Riba) is one of the gravest sins and is not permissible to engage in except out of dire necessity. The questioner must repent and seek forgiveness, and advise their father to repent. If the usurious borrowing occurred out of ignorance, then there is no sin upon them, as Allah Almighty says: "And there is no blame upon you for that in which you have erred, but [only for] what your hearts have intended." The principal of the usurious loan must be repaid, but the unlawful interest does not have to be repaid. As for the profits earned from the work, they are permissible, and the impermissibility lies only in borrowing with interest. The profit resulting from trade with a usurious loan is considered permissible property for the borrower, while still obligating repentance from dealing with usury.