Chapter: The Woman Suffering from Irregular Bleeding (al-Mustahada)

I heard Ishaq ibn Ibrahim say: 'The Sunnah of the Prophet, may Allah bless him and grant him peace, has passed down regarding the woman suffering from irregular bleeding in various aspects, due to the difference in their temperaments, and all of these [traditions] confirm one another. Those who do not have knowledge take them to be contradictory and differing.

Menstruation is a matter that cannot be grasped by intellects and analogies, because menstruation is a physical creation instilled in women, and they are not equal in that. Whoever understands what we have described and comprehends it will know that this is the case. How is it permissible for a scholar to make the menstruation of women a single matter, setting a time for them that they do not fall short of its minimum nor exceed its maximum, while it has become clear to him from the affairs of women what should have sufficed and satisfied him regarding our descriptions?! For they have known and perceived that the menstruation of women can be three, four, five, six, seven, eight, nine, and ten days, even though they know that the common [duration] of their menstruation (1) is six or seven [days], as the Prophet, may Allah bless him and grant him peace, described for Hamna bint Jahsh [the duration of] seven and six, saying to her: "Observe your menses as women observe their menses, and as they become pure according to the set time of their menses and their period of purity." We have heard of women who menstruate for two days and then become pure, just as women's purity occurs, or who menstruate for eleven days, or twelve days, or thirteen days, or fourteen days, or fifteen days. 
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 All of this has been authentically narrated from the scholars, and they have verified this from their women and others, to the extent that some of them said: "A woman from the women of the Majishun family menstruated for twenty days with a moderate menstruation." Malik ibn Anas and a number of the scholars of Medina rejected this, and they did not consider the time to be anything but fifteen days, making fifteen the final limit of the menstruating woman's time. Malik said: "A woman does not menstruate for more than half of her lifetime." Indeed, [the duration of] fifteen [days] has been authentically reported from more than one scholar, such as 'Ata' ibn Abi Rabah, and Malik ibn Anas after him, and [the duration of] thirteen [days] from Sa'id ibn Jubayr. Even al-Awza'i and Malik ibn Anas said: "There was a woman among us who would menstruate for a single day with a moderate menstruation."'