What is the ruling on taking money of questionable origin?

If the source of the money is unknown, the default assumption is that what a Muslim possesses is his property. However, if it is known that the money is stolen or usurped, it is not permissible to take it by any means, as it is the property of the wronged. If the owner of the money is known to have unlawful (haram) elements in his wealth, then piety dictates avoiding it. If the majority of his wealth is unlawful, there is a difference of opinion among scholars regarding it. As for a discreet Muslim, there is no doubt in dealing with him. If the suspicion of unlawfulness is not strong, there is no harm in dealing with him. But if it is strong, then piety dictates avoiding dealing with him and taking his money, based on the Prophet, peace and blessings be upon him, who said: "Whoever guards himself against doubtful things, he has indeed protected his religion and his honor."