Praise be to Allaah.
The Muslim woman must cover her entire body when praying, apart from her face, because her whole body is ‘awrah during prayer. According to the hadeeth, “Allaah does not accept the prayer of a woman who is of child-bearing age unless (she is covered) with a khimaar.” The cover must be ample and cover all the body, and it must be loose so that it does not show the shape of the body. It is sufficient for it to be one garment if it covers the body. As for the ruling on wearing pants or trousers, please see question no. 218388 .
Shaykh ‘Abd al-Kareem al-Khudayr.
We should point out here that there is no specific dress that is required for the Muslim woman to pray and that her prayer is invalid if she prays in any other garment, as many women in some Muslim societies think. Rather the ruling has to do with covering, so if she is covered properly, then her prayer is valid.