If these three signs are found together, then it is menstruation.

If these three signs are found together, then it is menstruation. These signs have been taken from a hadith of Im­am Ja'far as‑Sddiq (peace be upon him). A woman came to him and asked, "What should a woman do who sees blood on herself but does not know whether it is menstruation or some other type (of blood)?" The Im­am said, "The blood of menstruation is warm ...black (or dark‑coloured), and it has pressure and burning sensation..." The woman said, "By Allah!

If he had been a woman, he could not have added anything further in this (description)!"[^4] Duration Of Hayz The beginning of menstruation is determined when blood leaves the uterus and enters the vagina. It is necessary for the commencement of menstruation that the blood should be seen outside the vagina.

In another hadith, Imam as‑Sadiq said, "The minimum duration of menstruation is three days, and the maximum is ten days.”[^5] By "three days" we mean three days and the two nights between the first and the third day. For exam­ple, if blood starts on Monday morning and stops on Wednesday evening, then it is menstruation. And by "ten days" we mean ten days and the nine nights bet­ween the first and the tenth day. So, if a woman sees blood for less than three days, it is not considered hayz.

If the blood is seen for more than ten days, the ten days will be counted as menstrua­tion and the blood seen after that will be regarded as istihazah. The same Imam said, "The minimum duration of purity (between two menstrual cycles) must be (at least) ten days."[^6] So if a woman sees blood during the ten days after her period had ended, it will not be considered hayz.

Although it is normal to say that menstruation takes place once "a month", but it should be clarified that menstrual cycles take place every 28 days ‑ so, in the present context "a month" means a period of 28 days, not 29, 30 or 31 days. Different Categories Of Ha'iz According to the shari'ah, all the women are not same as far as the rules of menstruation are concerned.

By taking into consideration the difference in regulari­ty of time and days of monthly periods and their ir­regularity, women can be divided into three main groups: 1. Mubtadi'ah: literally, a beginner; in the present context it means a girl who sees menstruation for the first time. 2. Zatu 'l‑'adah: a woman who has menstruation regularly at a fixed time or for a fixed number of days or both.