Sahih al-Bukhari 146
صحيح البخاري#146SahihNarrated `Aisha:The wives of the Prophet (ﷺ) used to go to Al-Manasi, a vast open place (near Baqi` at Medina) to answer the call of nature at night. `Umar used to say to the Prophet (ﷺ) "Let your wives be veiled," but Allah's Apostle did not do so. One night Sauda bint Zam`a the wife of the Prophet (ﷺ) went out at `Isha' time and she was a tall lady. `Umar addressed her and said, "I have recognized you, O Sauda." He said so, as he desired eagerly that the verses of Al-Hijab (the observing of veils by the Muslim women) may be revealed. So Allah revealed the verses of "Al-Hijab" (A complete body cover excluding the eyes)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 4:12