Q: Many women do not strictly observe the code of dress while offering Salah (Prayer), as part of their arms, feet or even legs may be uncovered; is their Salah (Prayer) hence valid?
A: It is obligatory upon a free Mukallaf (person meeting the conditions to be held legally accountable for their actions) woman to cover all of her body except her face and hands when offering Salah, for all of her body is `Awrah (private parts of the body that must be covered in public).
If she offers Salah while some of her `Awrah such as her leg, feet, or head is uncovered, her Salah is not valid. The Prophet (peace be upon him) said: “Allah does not accept the Salah of a menstruating woman (i.e. an adult woman) unless (she covers her head) with a head-cover.” [Related by Ahmad and the Four Compilers of Hadith (Imams Abu Dawud, Al-Tirmidhy, Al-Nasa'y and Ibn Majah) except Al-Nasa'y through a Sahih (authentic) Sanad (chain of narrators)]The Prophet (peace be upon him) also said: A woman is `Awrah (i.e. her entire body must be covered). It is reported by Abu Dawud (may Allah be merciful with him) on the authority of Um Salamah (may Allah be pleased with her) that she asked the Prophet (peace be upon him) if a woman can offer Salah in a long dress and Khimar (veil covering to the waist) without Izar (garment worn below the waist).. The Prophet (peace be upon him) replied: This will be valid if the dress is long, covering all of her body, and covers the surface of her feet."
Al-Hafiz Ibn Hajar (may Allah be merciful with him) said in his book entitled Bulugh-ul-Maram: The scholars had classed this Hadith as an authentic Hadith Mawquf (words or deeds narrated from a Companion of the Prophet that are not attributed to the Prophet)) on the authority of Um Salamah (may Allah be pleased with her). If there is a man who is non-Mahram (not a spouse or an unmarriageable relative) present, she should cover her face and hands.