{ Oh Prophet, say to your wives and your daughters and the women of the believers to pull their outer garments over themselves; this is more suitable, that they may be recognized and not harmed } Al-Ahzab 59

‘Ali ibn Abi Talha related from Ibn ‘Abbas that Allah ordered the women of the believers, whenever they went out from their houses for a need, to cover their faces from the top of their heads with their outer garment [jilbab], showing one eye only. Muhammad ibn Sirin said: I asked ‘Ubaida Al-Salmani about the word of Allah Most High { Pull their outer garments over themselves } , and he covered his face and his head and showed just his left eye.
Regarding the word of the Most High { This is more suitable, that they may be recognized and not harmed } : that is, whenever they did this they would be recognized as being free women, not servant girls and not whores. Al-Suddi said regarding the word of the Most High { Say to your wives and your daughters and the women of the believers to pull their outer garments over themselves; this is more suitable, that they may be recognized and not harmed } ; he said: There were some of the lewd people of Medina who would go out to the city streets at nightfall to meddle with women. And quarters were tight, so the women would go out to the streets at night to fulfill their need, and these lewd men sought out the women. Whenever they saw a woman with a jilbab over her, they said: This one is a free woman, let her alone; and whenever they saw a women without a jilbab over her, they said: This one is a slave girl. And they would jump on her.