Is it permissible for a man to have intercourse with his wife if she sees a yellowish discharge, and she is at the beginning of her menstrual cycle, and what is incumbent upon him if he does so?

Yellowish discharge (ṣufrah) is considered menstruation if it occurs during the usual time of menstruation, or if it is connected to blood before purification (ṭuhūr). If sexual intercourse takes place during this period, it takes the ruling of sexual intercourse during menstruation, with all its associated consequences. However, if the yellowish discharge occurs after purification, it is not considered menstruation.