What is the ruling on believing a father who lies frequently about matters of food, drink, and clothing? And what is the ruling on letting him purchase these items, knowing that he works as a judge and may receive gifts or discounts? Is it obligatory to inquire about the source of everything he brings, or is it permissible to eat without asking? And is something considered unlawful if the father claims it is from a lawful source and explains its origin, but the questioner does not believe him due to his frequent lying?

It is not forbidden to deal with someone whose wealth is mixed unless the unlawful part of the wealth is specifically known. If you are in doubt about it, you are not obliged to inquire about it, relying on the principle of permissibility. The preponderant opinion is that dealing with someone whose wealth is mostly unlawful is disliked (makrooh). It is permissible to eat from a father's wealth if the unlawfulness stems from the method of earning, not from the money itself, and the sin falls solely upon the earner. This is supported by the action of the Prophet, peace and blessings be upon him, who ate from the wealth of the Jews, who were known for usury. The father should be advised gently and kindly if he has fallen into something unlawful.