What is the ruling on profits earned from investing money with a merchant whose source of profit is unknown, being somewhere between lawful and unlawful, knowing that the questioner is unable to take the more precautious approach?

If lawful and unlawful elements are mixed, and you do not know in which of them your money was invested, the jurists have stipulated that the ruling in this case is permissibility, and there is no harm upon you in benefiting from the profits, especially if the majority of his commercial activity is permissible.