Answer: The evidences are from Al-Qur’aan and Sunnah, (Allaah says in Al-Qur’aan): “And when you ask (his wives) for anything you want, ask them from behind a screen” [Al-Ahzab 33:53]. And hijab is that which covers the woman from dress or wall or door and the saying of Allaah: ”O Prophet! Tell your wives and your daughters and the women of the believers to draw their cloaks (veils) all over their bodies (i.e.screen themselves completely except the eyes or one eye to see the way), that will be better, that they should be known (as free respectable women) so as not to be annoyed.” [Al-Ahzab 33:59];
There is in the hijab a prevention of harm from the sinners who have a desire for them (women), if she is covered the sinners and hypocrites would not be tempted by her, and if she is uncovered then the sinners and hypocrites would be craving after her.
Ibn Abbaas (radiallaahu ‘anhu) was asked regarding the meaning of: “to draw their cloaks (veils) all over their bodies”, he then took the end of his thobe and placed it on his face signifying that this is it’s meaning; covering the face. And ‘Aa’isha (radiallaahu ‘anhaa) said: “We were with the Prophet (sallallaahu alayhi wa sallam) while in the state of Ihraam, if men pass by each of us we would lower our khimaar from the top of our heads to cover our face’s, and if they exceeded us we would remove the covering”.
And this was during the presence of the Prophet (sallallaahu alayhi wa sallam), while in agreement to what they (the women) were doing (he didn’t forbid them from what they were doing).
And hijab dear brothers, Allaah mentioned two benefits:
The first one is that it is a purification for the heart: That it is purer for your heart’s and for their heart’s, anyone from among the Muslims male or female want’s the purification of the heart (that’s why covering is better).
And the second benefit:
It prevents the harms of the hypocrites and sinners and their desires for her, if she covers herself in hijab they cannot see her face nor be tempted by her.
(Allaah says in the Al-Qur’aan): “That will be better, that they should be known (as free respectable women) it means; they are known as purified/ respectable women, so as not to be annoyed.” [Al-Ahzab 33:59], their (sinners or hypocrites) desires are cut-off by it, but if they see her uncovered displaying herself, they will seek her and eventually harm her (or hurt her).