Sahih al-Bukhari, Volume 8, Book 74, Hadith 255 (USC-MSA) ⓘ

Narrated Anas bin Malik: that he was a boy of ten at the time when the Prophet emigrated to Medina. He added: I served Allah's Apostle for ten years (the last part of his life time) and I know more than the people about the occasion whereupon the order of Al-Hijab was revealed (to the Prophet). Ubai b n Ka`b used to ask me about it. It was revealed (for the first time) during the marriage of Allah's Messenger with Zainab bint Jahsh. In the morning, the Prophet was a bride-groom of her and he Invited the people, who took their meals and went away, but a group of them remained with Allah's Messenger and they prolonged their stay. Allah's Messenger got up and went out, and I too, went out along with him till he came to the lintel of `Aisha's dwelling place. Allah's Messenger thought that those people had left by then, so he returned, and I too, returned with him till he entered upon Zainab and found that they were still sitting there and had not yet gone. The Prophet went out again, and so did I with him till he reached the lintel of `Aisha's dwelling place, and then he thought that those people must have left by then, so he returned, and so did I with him, and found those people had gone. At that time the Divine Verse of Al-Hijab was revealed, and the Prophet set a screen between me and him (his family).

حَدَّثَنَا يَحْيَى بْنُ سُلَيْمَانَ، حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي أَنَسُ بْنُ مَالِكٍ، أَنَّهُ كَانَ ابْنَ عَشْرِ سِنِينَ مَقْدَمَ رَسُولِ اللَّهِ صلى الله عليه وسلم الْمَدِينَةَ، فَخَدَمْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم عَشْرًا حَيَاتَهُ، وَكُنْتُ أَعْلَمَ النَّاسِ بِشَأْنِ الْحِجَابِ حِينَ أُنْزِلَ، وَقَدْ كَانَ أُبَىُّ بْنُ كَعْبٍ يَسْأَلُنِي عَنْهُ، وَكَانَ أَوَّلَ مَا نَزَلَ فِي مُبْتَنَى رَسُولِ اللَّهِ صلى الله عليه وسلم بِزَيْنَبَ ابْنَةِ جَحْشٍ، أَصْبَحَ النَّبِيُّ صلى الله عليه وسلم بِهَا عَرُوسًا فَدَعَا الْقَوْمَ، فَأَصَابُوا مِنَ الطَّعَامِ ثُمَّ خَرَجُوا، وَبَقِيَ مِنْهُمْ رَهْطٌ عِنْدَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَأَطَالُوا الْمُكْثَ فَقَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم فَخَرَجَ وَخَرَجْتُ مَعَهُ كَىْ يَخْرُجُوا، فَمَشَى رَسُولُ اللَّهِ صلى الله عليه وسلم وَمَشَيْتُ مَعَهُ حَتَّى جَاءَ عَتَبَةَ حُجْرَةِ عَائِشَةَ، ثُمَّ ظَنَّ رَسُولُ اللَّهِ صلى الله عليه وسلم أَنَّهُمْ خَرَجُوا فَرَجَعَ وَرَجَعْتُ مَعَهُ، حَتَّى دَخَلَ عَلَى زَيْنَبَ فَإِذَا هُمْ جُلُوسٌ لَمْ يَتَفَرَّقُوا، فَرَجَعَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَرَجَعْتُ مَعَهُ، حَتَّى بَلَغَ عَتَبَةَ حُجْرَةِ عَائِشَةَ، فَظَنَّ أَنْ قَدْ خَرَجُوا، فَرَجَعَ وَرَجَعْتُ مَعَهُ، فَإِذَا هُمْ قَدْ خَرَجُوا، فَأُنْزِلَ آيَةُ الْحِجَابِ، فَضَرَبَ بَيْنِي وَبَيْنَهُ سِتْرًا‏.‏