Sahih al-Bukhari, Volume 6, Book 60, Hadith 317 (USC-MSA) ⓘ

Narrated Anas: When Allah's Messenger married Zainab bint Jahsh, he made the people eat meat and bread to their fill (by giving a Walima banquet). Then he went out to the dwelling places of the mothers of the believers (his wives), as he used to do in the morning of his marriage. He would greet them and invoke good on them, and they (too) would return his greeting and invoke good on him. When he returned to his house, he found two men talking to each other; and when he saw them, he went out of his house again. When those two men saw Allah's Messenger: going out of his house, they quickly got up (and departed). I do not remember whether I informed him of their departure, or he was informed (by somebody else). So he returned, and when he entered the house, he lowered the curtain between me and him. Then the Verse of Al-Hijab was revealed.

حَدَّثَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ بَكْرٍ السَّهْمِيُّ، حَدَّثَنَا حُمَيْدٌ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ أَوْلَمَ رَسُولُ اللَّهِ صلى الله عليه وسلم حِينَ بَنَى بِزَيْنَبَ ابْنَةِ جَحْشٍ فَأَشْبَعَ النَّاسَ خُبْزًا وَلَحْمًا ثُمَّ خَرَجَ إِلَى حُجَرِ أُمَّهَاتِ الْمُؤْمِنِينَ كَمَا كَانَ يَصْنَعُ صَبِيحَةَ بِنَائِهِ فَيُسَلِّمُ عَلَيْهِنَّ وَيَدْعُو لَهُنَّ وَيُسَلِّمْنَ عَلَيْهِ وَيَدْعُونَ لَهُ فَلَمَّا رَجَعَ إِلَى بَيْتِهِ رَأَى رَجُلَيْنِ جَرَى بِهِمَا الْحَدِيثُ، فَلَمَّا رَآهُمَا رَجَعَ عَنْ بَيْتِهِ، فَلَمَّا رَأَى الرَّجُلاَنِ نَبِيَّ اللَّهِ صلى الله عليه وسلم رَجَعَ عَنْ بَيْتِهِ وَثَبَا مُسْرِعَيْنِ، فَمَا أَدْرِي أَنَا أَخْبَرْتُهُ بِخُرُوجِهِمَا أَمْ أُخْبِرَ فَرَجَعَ حَتَّى دَخَلَ الْبَيْتَ، وَأَرْخَى السِّتْرَ بَيْنِي وَبَيْنَهُ وَأُنْزِلَتْ آيَةُ الْحِجَابِ‏.‏ وَقَالَ ابْنُ أَبِي مَرْيَمَ أَخْبَرَنَا يَحْيَى حَدَّثَنِي حُمَيْدٌ سَمِعَ أَنَسًا عَنِ النَّبِيِّ صلى الله عليه وسلم‏.‏