What should you do about gold whose source you doubt, and your mother confirms she bought it?

The default is to believe the mother's statement that she bought the gold, and there is no harm in using it. However, if there is a strong suspicion, due to circumstantial evidence, that its source is unlawful, then using it becomes disliked. It can be disposed of or returned to the mother in a way that does not anger her, in accordance with the Prophet's (peace be upon him) saying: "Leave that which makes you doubt for that which does not make you doubt."