Is the money of a servant who repents permissible for his heirs?

Repentance does not make the unlawful lawful. Among the conditions for the validity of repentance from injustices is to return what was taken to its rightful owners or to give it as charity on their behalf. If the money was acquired through unlawful means, such as usury (riba) or the sale of prohibited items, it must be disposed of by spending it on the interests of Muslims or giving it to the poor and needy. If the amount of the unlawful gain is unknown, one should estimate it and disburse it. Repentance removes the sin of the previous transgression, but it does not render the money lawful. The proof for this is Allah’s saying: "And if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged."