What is the ruling for a woman who has no established cycle or distinguishing sign (Mubtadi'ah) and begins menstruating?
Chapter on Menstruation
Al-Mughni
Book of Purification
Primary text
The well-known opinion from Ahmad concerning the one who has no established cycle or distinguishing signs, meaning menstruation has just begun for her, is that she refrains from prayer and fasting upon seeing the blood, provided she is of an age where menstruation is possible (nine years old and upward). If the bleeding continues beyond one day and one night, she performs Ghusl immediately thereafter, performs Wudu for the time of each prayer, prays, and fasts.
Supporting text
If the bleeding stops at the maximum duration of menstruation or less, she performs a second Ghusl upon cessation and repeats this process in the second and third months. If the number of bleeding days is equal across these three months, that duration becomes her established cycle. It is then known that this was menstruation, and she must make up any obligatory fasting performed during that time because it is established that she fasted during her menses.