Is it permissible to benefit from a well dug by one's father with the money from a car whose odometer he tampered with in order to increase its price?

If your father sold the car with some deceit, then a portion of its price, equivalent to the extent of the deceit, becomes unlawful for him. The car's price is a mixture of lawful and unlawful elements. If he dug a well with part of its price, there is no harm in benefiting from it, as the unlawful portion in the well is not specifically identifiable. The majority of scholars permit dealings with someone who possesses mixed wealth, albeit with some disapproval, as long as the dealing is not directly with the unlawful part of his wealth. If he dug the well with the entire price, this does not necessarily mean that benefiting from the well is unlawful, because the unlawfulness pertains to the liability of the deceiver, not to the specific object of his wealth. Therefore, there is no harm for you in benefiting from it. However, you should advise your father by explaining the unlawfulness of his action and the obligation to extract the amount corresponding to the percentage of deceit in the car's price, for the Prophet, peace and blessings be upon him, said: "If they are truthful and make clear, they will be blessed in their transaction. If they lie and conceal, the blessing of their transaction will be effaced."