Is sexual intercourse with one's wife after the discharge of yellowish-white or brown secretions two days before menstruation, followed immediately by the onset of menstruation after intercourse, considered intercourse during menstruation?

If the aforementioned fluid appeared before your wife's usual menstrual period, it is considered menstruation, as it falls under the ruling of yellowish or brownish discharge during the time of menstruation. This is based on the statement of Umm Atiyyah (may Allah be pleased with her): "We did not consider yellowish or brownish discharge as anything significant," and Abu Dawud added: "after purification."

If its appearance is outside the usual time of menstruation, then there is no harm.

However, if the discharge occurs at the usual time of menstruation, it is considered menstruation, and you must repent to Allah, as He has forbidden intercourse with a menstruating woman, saying: {And they ask you about menstruation. Say, "It is a discomfort." So keep away from women during menstruation. And do not approach them until they have purified themselves.} Some scholars are of the view that whoever has intercourse with a menstruating woman must pay an expiation of one dinar or half a dinar.