Mukhtasar Bukhari

Narrated from Ummul Momineen Aisha Siddiqa Tayyiba Tahira (may Allah be pleased with her) that when the wives of the Prophet Muhammad (peace be upon him) would go out at night for relieving themselves, they would go towards Manasi’ (which means a spacious mound). Sayyiduna Umar (may Allah be pleased with him) used to say to the Prophet Muhammad (peace be upon him) that you should make your wives observe veiling, but the Messenger of Allah (peace be upon him) did not do so. Then one night at the time of Isha, Ummul Momineen Sawda (may Allah be pleased with her), that is, the wife of the Prophet Muhammad (peace be upon him), went out and she was a tall woman. Umar (may Allah be pleased with him), out of the desire that the command of veiling be revealed, called out, “Be aware, O Sawda! We have recognized you.” So Allah the Exalted revealed the command of veiling.