From which sources are the conditions for Islamic dress (that it does not "define" and is not transparent and is not adornment) derived, although Allah, the Exalted, says (what means): {... and not expose their adornment except that which [necessarily] appears thereof...} [Quran 24:31], and some commentators stated that the (necessarily appearing adornment) refers to the clothes?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is no doubt that the rationale behind the divine imperative for Muslim women to cover their ‘Awrah (body parts which must be covered) and adhere to the Hijab is to close off the means that leads to falling into Fitnah (temptation). This cannot be achieved if the woman wears transparent clothing that reveals the color of her skin or outlines the ‘Awrah and defines its shape.

It has authentically been reported that the Messenger of Allah, forbade women from wearing such a kind of clothing as he said: "… and women who are clothed yet naked." [Muslim]

An-Nawawi commented on this Hadeeth saying, "It refers to such a woman who wears transparent clothes that reveal the color of her skin."

Moreover, Umm Salamah reported that the Prophet, sallallaahu ‘alayhi wa sallam, said: "How many (people) are clothed in this world, yet naked in the Hereafter!" [Al-Bukhari]

Al-Haafith Ibn Hajar said:

"This Hadeeth refers to the fact that the Prophet did not wear transparent clothes because given that he warned those who wear them of having their ‘Awrah exposed, he was more likely to have the qualities of perfection than anyone else."

Hence, it is clear that the conditions of the Islamic Hijab were derived from the sayings and acts of the Prophet.

Allah Knows best.