What is the ruling on one who had intercourse with his wife while she had blood, not knowing if it was menstruation or bleeding, and the blood appeared 10 days before the due date of her period due to a medication that causes intermenstrual bleeding?

If blood appears after 15 days of purity and continues for a day and a night or more, it is considered menses, even if it comes before its usual time due to medication. The menstruating woman is prohibited from whatever she is normally prohibited from during menses. If intercourse occurs out of ignorance, there is no sin or expiation according to the majority of scholars. However, the Hanbalis hold that it is obligatory to give half a dinar in charity as expiation, whether it was intentional or out of ignorance, but this expiation is waived if one is unable to pay. What is incumbent upon the husband is also incumbent upon the wife if she is compliant, and there is nothing upon her if she was coerced.