Hadeeth on Hijab

‘A’isha reported that;

the wives of Allah’s Messenger (may peace be upon him) used to go out under the cover of night when they went to open fields (in the outskirts of Medina) for easing themselves. ‘Umar bin Khattab used to say: Allah’s Messenger, ask your ladies to observe veil, but Allah’s Messenger (may peace be upon him) did not do that. So there went out Sauda, daughter of Zarn’a, the wife of Allah’s Messenger (may peace be upon him), during one of the nights when it was dark. She was a tall statured lady. ‘Umar called her saying: Sauda, we recognize you. (He did this with
the hope that the verses about the veil would be revealed.) ‘A’isha said: Allah, the Exalted and Glorious, then revealed the verses pertaining to the veil.
(Muslim, Book 26: Hadith 5397 )