A woman never acts on the discernment of the different types of blood unless her bleeding exceeds the maximum period of ḥayḍ. Also, if her habit changes, she acts on the new habit, as long as it does not exceed the longest period of ḥayḍ. When the bleeding stops even for a short while (down to 1 hour), the woman must make ghusl and resume her worship. If it recurs within the time of ḥayḍ, she refrains again, and so on. If the bleeding takes place on some days and skips others, she will consider herself pure in the intervening days without bleeding. In these days, all worship is permissible, and so is intercourse. If she is a beginner, and she bleeds every other day for 18 days, then she will consider the menstruation to be all the days of bleeding within the first 15 days, and the rest will be istiḥâḍah (non-menstrual vaginal bleeding). If she is not a beginner, then her ḥayḍ will be the days of bleeding within her customary ḥayḍ period; if she has not established a habit, then the days of the dark odorous blood; and if she is not discerning, then the days of bleeding within the first 7 days, so if she was bleeding every other day, then her ḥayḍ will be days 1, 3, 5, and 7 only, according to the stronger position. Days 9, 11, 13, 15, and 17 will be all considered istiḥâḍah (non-menstrual vaginal bleeding). The shortest period of purity is 13 days. If a woman’s cycle occurs every 20 days, and she is not discerning, nor did she have a habit from before, then she will consider the first 7 days her ḥayḍ and the following 13 days to be pure (istiḥâḍah, or non-menstrual bleeding). If the cycle is repeated more frequently than this, she will keep the days of purity fixed at 13; so in an 18-day cycle, she will consider only the first 5 days as her ḥayḍ.