Nisaa
Hayd occurs when women are going through menstrual bleeding. Menstrual blood has distinct characteristics: it is dark in color, thick in consistency, and has a distinct odor different from ordinary blood. The Prophet (Salla Allahu Alayhi Wa Sallam) said to Fatimah bint Abi Hubaysh: “When it is menstrual blood it is dark and recognizable, so when it is like that, then stop praying, and when it is otherwise, do wudu and pray, for that is from a vein.” (Narrated by Abu Dawud and al-Nasai; classed as sahih by Ibn Hibban and al-Hakim). If you observe this type of blood, it signifies your menses.
Regarding the duration of period, scholars differed.
Some scholars considered that there is no minimum or maximum number of days for Hayd, as there is no clear evidence in the Quran and Sunnah specifying a limit, as long as there is nothing indicating that it is Istihadah. This was the view of some scholars such as Sheikh al-Islam Ibn Taymiyyah.
Other scholars have defined a minimum and/or maximum number of days for Hayd based on customary practice and observed experiences of women, though these limits vary across the four madhhabs.
Minimum duration:
- Malikis: no set minimum (even one gush).
- Hanbalis & Shafi'is: one day and one night.
- Hanafis: minimum three days.
Maximum duration:
- Hanafis: ten days.
- Shafi'i, Maliki, Hanbali: fifteen days. Anything beyond that is Istihadah.
Malikis also differentiate between a girl’s first-ever period and women who have already menstruated before. For the first period, up to 15 days can be considered Hayd. For later cycles, the maximum is her previously known longest Hayd + 3 days, not exceeding 15 days.
Most scholars agree that menstruation generally does not exceed 15 days, and the period of purity cannot be shorter than menstruation.