Is it permissible to benefit from the wealth of a deceased father if it is mixed with earnings from usury?

Wealth acquired through illicit means, such as usury (riba), does not become permissible for the heirs upon the death of the acquirer. They must extract the forbidden portion from the inheritance. If the exact amount is unknown, they should strive to estimate it, or donate half of it to the poor and needy. If the heirs themselves are poor, it is permissible for them to take from it an amount sufficient for their needs. Some scholars are of the view that unlawful wealth, due to its acquisition and not its intrinsic nature, is forbidden only for the acquirer, not for their heirs.