What is the ruling on disposing of commingled money, the principal of which is lawful with its earnings, when it is unknown whether the assistance provided from it is from the principal or from its earnings?

It is permissible to accept a gift or salary from someone whose wealth is mixed with both lawful and unlawful components. The Prophet, peace and blessings be upon him, used to interact with and accept gifts from polytheists, Jews, and others, whose wealth was mixed. It is incumbent upon anyone who wishes to benefit from a portion of mixed wealth to intend that it be from the lawful part.