Ruling on praying
    in a torn garment
Question

                If one fnds a hole in their prayer garment, and realizes that he/she has
      been praying in such a condition (the 'awra could be seen through the hole) for some time,
      are all of his/her prayers in need of being repeated? If so, and the person does not know
      for how long this occurred, how can they be sure they made up enough prayers?
Praise be to Allah.The scholars, may Allaah have mercy on them, agreed that covering the
    awrah is a condition of the validity of ones prayer. The evidence for this is
    the aayah (interpretation of the meaning): O Children of Adam! Take your
    adornment (by wearing your clean clothes) while praying [al-Araaf 7:31]
The conditions for clothes to cover the awrah properly are as
    follows:
They should not show the shape or contours of the body; if they do so,
        this is no good because it does not cover properly.
They should be clean (taahir). If the clothes are unclean or impure
        (naajis), then it is not correct to pray in them, because it is haraam to have any
        impurity (najaasah) on ones body or clothes when praying. Allaah says
        (interpretation of the meaning): And your garments purify! [al-Muddaththir
        74:4]. It was reported that a baby boy who was not yet eating solid food was brought
        to the Prophet 
 (peace and blessings of Allaah be upon him), and he sat the infant in his
        lap. The child urinated in his lap, and he called for water and poured it over the urine.
        The fact that the Prophet 
 (peace and blessings of Allaah be upon him) hastened to wash
        the childs urine from his clothes indicates that it is obligatory to clean
        ones clothes of any impurity that may get on them.
They should be permissible, not haraam, whether they are haraam in and
        of themselves, such as silk garments, or because of the way in which they are made, such
        as garments that come below the ankles, or because of the way in which they were acquired,
        such as garments seized by force or stolen. 
With regard to the matter of the awrah becoming uncovered during
    prayer, al-Shaafa'i, may Allaah have mercy on him, said: It is good enough for both
    men and women to pray with their awrah covered. The mans awrah is what I
    have already described (i.e., from the navel to theknee), and all of a woman is awrah, apart from her
    face and hands. The top of her feet is also awrah. If during prayer any part of the
    area between a mans navel and knees becomes uncovered, or any part of a womans
    hair, whether it is a lot or a little, or any part of her body apart from her face and
    hands and wrist  and no more than that  becomes uncovered, whether they
    realize it or not, then both (man and woman) must repeat the prayer  unless it was
    uncovered by the wind, or it slipped and was immediately replaced without delay (no longer
    than it takes to pick up the garment and place it back immediately.) (Al-Shaafa'i, Kitaab
    al-Umm, Baab Kayfiyyat Libs al-Thiyaab fil-Salaah). 
Ibn Qudaamah (may Allaah have mercy on him) said in his book al-Mughni:
    Section: if a little bit of the awrah becomes uncovered, this does not
    invalidate the prayer. This is the opinion of Ahmad and Abu Haneefah. Al-Shaafa'i said:
    It invalidates the prayer because it is a ruling that has to do with the
    awrah, and it is the same whether it is a little or a lot, as is the case with
    looking (at the awrah). We have what was reported by Abu Dawood, with his
    isnaad from Ayyoob, from Amr ibn Salamah al-Jarmi, who said: My father went
    with a group from his people to the Messenger of Allaah 
 (peace and blessings of Allaah be
    upon him), and he taught them how to pray. He said, The one who reads Quraan
    best among you should lead you in prayer. I was the best at reading Quraan, so
    they appointed me. I used to lead them in prayer wearing a small yellow burdah (cloak or
    garment), and when I prostrated, my awrah became uncovered. One of the women said,
    Cover the awrah of your reciter for us! so they bought me an Omani
    shirt, and I never rejoiced over anything  apart from Islam  as much as I
    rejoiced over that. Reported by Abu Dawood. Al-Nasaa'i also reported from
    Aasim al-Ahwal, from Amr ibn Salamah, who said: I used to lead them in
    prayer wearing a burdah made of two attached parts in which there was a gap. When I
    prostrated in it, my backside showed. This was common and was not denounced, and we
    have not heard that the Prophet 
 (peace and blessings of Allaah be upon him) or any of his
    Companions denounced it, because if prayer is still valid despite a severe problem where
    there is an excuse, then we should differentiate between whether the problem is severe or
    not where there is no excuse; it is like the case of walking during the prayer. Avoiding
    little matters may be too difficult, so a little is excused, as is the case with blood.
    Once this is clear, the definition of a lot is that which is offensive to look at, and in
    this case there is no differentiation between the private parts and other parts of the
    awrah. A little is that which is not offensive, and the point of reference is that
    which is customary, except that the two private parts are more offensive than anything
    else, so that is considered to be an obstacle to prayer This is a matter in which
    Islam did not define what is offensive, so the point of reference is what is customary, as
    also applies in the case of excessive movement during the prayer
If these holes show what is customarily regarded to be too much of the
    awrah, and it shows it for a while, or it is not possible to cover them because the
    garment is too small, for example, then the prayer is not valid, because covering the
    awrah is one of the conditions of prayer, and if one of the conditions is not met
    without a valid excuse such as inability to meet it, then the prayer is not valid. You
    have to repeat the prayers which you did wearing this garment. If you do not know how many
    they were, you should take what you are certain of. For example, if you think that they
    may have been four or three or five, but definitely not more than five, then what you can
    be certain of in this case is five, and so on. And Allaah knows best.