حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ أَيُّوبَ، عَنْ أَبِي قِلاَبَةَ، قَالَ أَنَسُ بْنُ مَالِكٍ أَنَا أَعْلَمُ النَّاسِ، بِهَذِهِ الآيَةِ آيَةِ الْحِجَابِ، لَمَّا أُهْدِيَتْ زَيْنَبُ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم كَانَتْ مَعَهُ فِي الْبَيْتِ، صَنَعَ طَعَامًا، وَدَعَا الْقَوْمَ، فَقَعَدُوا يَتَحَدَّثُونَ، فَجَعَلَ النَّبِيُّ صلى الله عليه وسلم يَخْرُجُ، ثُمَّ يَرْجِعُ، وَهُمْ قُعُودٌ يَتَحَدَّثُونَ، فَأَنْزَلَ اللَّهُ تَعَالَى ‏ end actual hadith container 2‏ إِلَى قَوْلِهِ ‏ end actual hadith container 1‏ فَضُرِبَ الْحِجَابُ، وَقَامَ الْقَوْمُ‏.‏

Narrated Anas bin Malik: I of all the people know best this verse of Al-Hijab. When Allah's Messenger (PBUH) married Zainab bint Jahsh she was with him in the house and he prepared a meal and invited the people (to it). They sat down (after finishing their meal) and started chatting. So the Prophet (PBUH) went out and then returned several times while they were still sitting and talking. So Allah revealed the Verse: 'O you who believe! Enter not the Prophet's houses until leave is given to you for a meal, (and then) not (so early as) to wait for its preparation .....ask them from behind a screen.' (33.53) So the screen was set up and the people went away. Translation Not Available

Book Ref: Sahih Bukhari Book 65 Hadith 4792
Web Ref:  Sahih Bukhari Vol 6 Book 60 Hadith 315