What is the ruling regarding purity following a cessation of menstrual blood?
Chapter on Menstruation
Al-Mughni
Book of Purification
Primary text
Upon seeing a period of purity (tuhur), the woman is pure, must perform ghusl (ritual bath), and is then obligated to perform prayer and fasting. Our scholars (Ashabuna) do not differentiate between a short or long period of purity, based on the saying of Ibn Abbas: 'As for what she sees of purity for an hour, she must perform ghusl.'
Supporting text
It is considered that if the cessation of blood is less than a full day, it is not considered a period of purity, based on the narrations regarding post-natal bleeding (nifas) where anything less than a day is disregarded. This is the sounder opinion, as requiring ghusl for only an hour of purity followed by renewed bleeding imposes undue hardship, which is negated by the Quran (Quran 2:78). Furthermore, treating a short cessation as purity would prevent the establishment of a fixed menstrual cycle. Thus, cessation of blood less than a day is not purity unless there is an indicator such as the bleeding ceasing at the end of her normal habit duration or the appearance of al-Qassah al-Bayda' (the white discharge).