What is the ruling on a worker working for a person whose establishment was founded with usurious money, and is the money he earns unlawful?

It is impermissible to deal with someone whose entire wealth is known with certainty to be unlawful (haram), and this includes sales, settling debts, and other transactions. A worker should not undertake work with someone whom he knows to have an illicit source of wealth. If such a situation arises, he must ensure that his wages come from lawful (halal) money. If he is not paid his due except from unlawful wealth, then it is forbidden for him to work with that person, and he must spend the wages on general public welfare for Muslims or give them as charity to the poor and needy. It is not permissible for him to own those wages. However, if some of the wealth is lawful and some is unlawful, then there is another detailed ruling for that.