Shaykh Al-Islaam Ibn Taymiyyah said:
“The khimaar (which a woman is obliged to cover herself with) is that which covers the head, the face and the neck. And the jilbaab is that which is made to fall from the top of the head downwards, such that oohing from her dress is apparent except for her two eyes.”
[As is reported on him by Al-Albaanee in his book “Hijaab” p.71]