A woman is commanded to cover her hair with a veil when she prays by herself in her house, whereby she is allowed to expose it outside the salât. Therefore, it is the Right of Allâh on us to take an adornment when praying.
No one has the right to circumambulate the Ka’bah nakedly even if he is alone in darkness where no one can see him. Likewise, it is not permissible for him to pray nakedly even if he is by himself.
It is from this point that we understand that, taking of an adornment in salât, is not for the purpose of veiling from people. Doing that is one thing and veiling from people is another thing. Also, it is understood that, an individual may cover in salât that which is permissible for him to expose outside the salât, and a woman may expose in salât that which she covers from the sight of men.
The example of the first issue is like that of the shoulders. For verily the Prophet (Sallalaahu Alaihi wa Sallam), has forbidden one of us to pray in one cloth that covers not his shoulders this is because it is the right of salât that one covers his shoulders when he prays though it is permissible for him to expose his shoulders to men outside the salât.
Likewise the free woman, it is a must on her to put on a head-covering when praying as the Prophet (Sallalaahu Alaihi wa Sallam), said:
“لاَ يَقْبَلُ اللهُ صَلاَةَ حَاءِضٍ إِلاّ بِخِمَارٍ”
“Allâh the Almighty will not accept the prayer of the woman who reached puberty except with a head-covering” though it is not upon her to put on Khimâr [i.e., head-covering] whenever she is with her husband or her family members. That is because it is permissible for her to expose the hidden adornment to them, but it is not permissible for her to expose her head when praying, neither to her family members nor other than them.
And the opposite of that are the face, the hands and the feet. It is impermissible for her to expose these parts to foreign men according to the most correct opinion. Contrary to what was before the abrogation of that rule, as a matter of fact, she is only allowed to expose her garment. But as for covering those parts [face, hands and feet] in salât, it is not obligatory according to the consensus of the scholars though they are from the hidden adornment. But as for the ruling of the hands, the majority of the scholars like Abu Haneefah, Shafi’ee and others, have agreed upon the permissibility of exposing them in salât. And this is one of the narrations of Imam Ahmad. Also, according to Abu Haneefah it is permissible to expose the feet when praying, and this is the strongest opinion; because Ayesha has considered it from the apparent adornment.
 It is agreed upon. And it is emanated in “Sahih Abi Dawud”  and “Ir’waa Al-Ghalil” .
 I said: Particularization of Khimâr to the free woman is of the issues that has no proof for it. Rather, the generality of the following Hadith negates that. And look in the previous comment.
Taken from “The Veil of The Muslim Women and Her Dress in Salat” – by Sheikh-ul-Islâm Ibn Taymiyyah which has its verification by the Muhaddith of our times Sheikh Muhammad Nasrideen Al-Albaani may Allâh have mercy on them both.
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