Praise be to Allah.
The Qur’aan and Sunnah both direct women to cover themselves and avoid displaying their adornments in front of “strangers” (non-mahram men). The Qur’aan tells the Prophet (peace and blessings of Allaah be upon him) (interpretation of the meaning):
“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. And Allâh is Ever Oft-Forgiving, Most Merciful” [al-Ahzaab 33:59].
Allaah commanded His Prophet (peace and blessings of Allaah be upon him) to start by telling his wives and daughters to wear the jilbaab (i.e., the abaayah or an outer garment), because he and his family are examples for the believing men and women, then he was to command the believing women to do likewise:
“That will be better, that they should be known (as free respectable women) so as not to be annoyed” means, if a woman wears the jilbaab, it will be known that she is a decent woman who covers herself and desires chastity, unlike the women of the Jaahiliyyah who uncovered their adornments and temptations in front of all men, so she herself would be tempted and she would tempt others, she was misled and she misled others, as the Prophet (peace and blessings of Allaah be upon him) described them in the hadeeth narrated by Muslim:
“There are two types of the people of Hell whom I have not seen: men with whips like the tails of cattle with which they strike the people, and women who are clothed but naked, walking with an enticing gait, with something like the humps of camels on their heads. They will not enter Paradise nor even smell its fragrance, and its fragrance can be smelled from such and such a distance.”
The Messenger (peace and blessings of Allaah be upon him) also warned against having too relaxed an attitude towards the matter of women mixing with men who are not her mahrams, or who are only temporarily her mahrams, like her sister’s husband or her husband’s brother and so on. He (peace and blessings of Allaah be upon him) said: “Beware of entering upon women.” They said, “O Messenger of Allaah, what do you think about the brother-in-law?” he said: “The brother in law is death.” I.e., many people have a relaxed attitude towards the brother-in-law entering upon women, until some disaster happens as a result, that they never thought would happen because they trusted their brother-in-law! This is neglecting reality, because no man is alone with a (non-mahram) woman but the Shaytaan is the third one present with them, and no woman is exposed to temptation but she will give in, except for those on whom Allaah has mercy. We ask Allaah to keep us all safe from that, and to help us follow His words (interpretation of the meaning):
“And all of you beg Allaah to forgive you all, O believers, that you may be successful” [al-Noor 24:31]