Al-Imām al-Bukhārī - upon whom be mercy - narrates: Yaḥyā ibn Bukayr related to us; he said: al-Layth related to us; he said: ‘Uqayl related to me, from Ibn Shihāb, from ‘Urwah,
from our mother ‘Ā’ishah (may Allāh Almighty be content with her), who said: The wives of the Messenger of Allāh ﷺ would go out at night to al-Manāṣi’ in order to relieve themselves. Al-Manāṣi’ refers to wide, open areas. She said: ‘Umar - may Allāh Almighty be content with him - used to say to the Messenger of Allāh ﷺ: “Observe strict veiling for your wives.” However, the Messenger of Allāh ﷺ did not initially act upon this. Then one night, our mother Sawdah bint Zam’ah - may Allāh Almighty be content with him - went out after the night prayer to relieve herself. She was a tall woman, and ‘Umar - may Allāh Almighty be content with him - called out to her, saying: “O Sawdah! We have recognised you!” ‘Umar - may Allāh Almighty be content with him - was eager that the ruling of ḥijāb be revealed. Thereafter, Allāh Most High revealed the verse commanding ḥijāb.
Reference: Sahih Al Bukhari 146