What is the Sharīʿah ruling on a husband having intercourse with his wife on the sixth day of her menstrual cycle, knowing that blood appeared a few seconds before ejaculation? Is the husband sinful, and what is incumbent upon him?

If you continued to have intercourse with your wife after becoming aware of her menstruation and did not immediately withdraw, you have sinned. However, if you promptly withdrew as soon as you became aware of her menstruation, there is no sin upon you. If you have sinned, the majority of scholars hold that you only need to repent, whereas the Hanbalis believe that expiation is obligatory, and this latter opinion is more cautious and more absolving of responsibility.