Please my sister asks me, why is that women doing pray when they are in their period (menses). I don't know what to tell her.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

It is forbidden for a woman in menstruation to perform the prayer according to the texts [from the Book of Allaah or the Sunnah of the Prophet ] and the consensus of the scholars. The reason is that purity is one of the conditions for the validity of the prayer as the Prophet said: "Prayer is not valid without ablution [without being in a state of purity]." [Muslim] So it is not possible for a woman to be pure in a state menstruation.

If it is argued why a woman is prevented from fasting, and purity is not a condition for the validity of fasting, then the answer to this is that she is not allowed to fast while is menstruation because fasting weakens the body. Besides, when a woman is in menses, she is usually in pain and suffers from gripes and so forth. So if these two things are combined together, then this harms her body and weakens her, so it is a Mercy from Allaah that when a woman is in menses, she is not allowed to fast.

One of the Shaafi'ee scholars said: 'A servant is always required to abide by the Commandments of Allaah and the ruling of the Prophet whether or not one knows the wisdom behind such commandments; as Allaah says (which means): {It is not for a believing man or a believing woman, when Allaah and His Messenger have decided a matter, that they should [thereafter] have any choice about their affair. And whoever disobeys Allaah and His Messenger has certainly strayed into clear error.}[Qur'an 33:36].'

It is for this reason that when 'Aa'ishah was asked: "Why is it that a menstruating woman is required to make up for the fasting but she is not required to make up for the prayer?"; she replied: "When we were in menstruation we were ordered to make up for the fasting but we were not ordered to make up for the prayer." So she gave the religious ruling regardless of knowing or ignoring the wisdom behind such a ruling.

Allaah knows best.