What is the ruling on brown discharge that appears after clear blood and continues for up to 15 days? Is it menstruation or istihadah (non-menstrual bleeding)? Is it permissible to pray, engage in sexual intercourse, and fast while it is present? And must clothes soiled by it be changed before ablution?

Brown discharge connected to menstrual blood is considered menstruation and prohibits prayer, as the color of blood may change at the end of menstruation, and may be followed by yellowish or brownish discharge. Purity is not attained except by seeing "the white discharge" (al-qassah al-bayda') or complete dryness of the area. If it continues to flow with clear blood for 15 days, all of it is considered menstruation, because the maximum duration of menstruation is fifteen days. However, if it appears after seeing a sign of purity, it is not considered menstruation. Brown discharge is impure, but it is not obligatory to wash it or change clothes because of it, except when praying or similar acts for which purity is required.