Fatwa ID: 02020
Answered by Mufti Mohammed Tosir Miah
Can a woman offer prayer in shirt which is loose and long enough to cover her awrah?
Muslim women should refrain from wearing revealing, transparent clothing that allows their bodies to become visible for all to see.
Saaiduna Abu Huzaifah narrates that the Prophet of Allah said “There are two types of the dwellers of Hell whom I did not see. People having flogs like the tails of the Ox and they would be beating people with them and the women who would be dressed but appear to be naked, who would be inclined to evil and make their husbands incline towards it. Their heads would be like the humps of the bukht camel inclined to one side. They would not enter paradise and they would not smell its odour, whereas its odour would be smelt from such and such distance.” (Sahih Muslim p.205 v.2)
The awrah (area which needs to be covered for Salah) for a woman is her full body including her descending hair according to the correct opinion, except for the face, hands and feet”. (Raddul Muhtar p.77 v.2) The awrah must be concealed from before entering into Salah and must remain concealed until the end. If quarter of a part or organ that requires concealment is exposed intentionally, then the Salah will not be valid. If however, quarter of the organ, which is included in the Awra, becomes exposed during Salah, then, if this remains to the duration of three Subhan Allah, Salah will become invalid. (Nurul Idah p.123)
With regards to your question, as long as the shirt is loose and covers the awrah the Salah will be valid.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham