Sahih al-Bukhari, Volume 7, Book 62, Hadith 95 (USC-MSA) ⓘ

Narrated Anas bin Malik: I was ten years old when Allah's Messenger arrived at Medina. My mother and aunts used to urge me to serve the Prophet regularly, and I served him for ten years. When the Prophet died I was twenty years old, and I knew about the order of Al-Hijab (veiling of ladies) more than any other person when it was revealed. It was revealed for the first time when Allah's Messenger had consummated his marriage with Zainab bint Jahsh. When the day dawned, the Prophet was a bridegroom and he invited the people to a banquet, so they came, ate, and then all left except a few who remained with the Prophet for a long time. The Prophet got up and went out, and I too went out with him so that those people might leave too. The Prophet proceeded and so did I, till he came to the threshold of `Aisha's dwelling place. Then thinking that these people have left by then, he returned and so did I along with him till he entered upon Zainab and behold, they were still sitting and had not gone. So the Prophet again went away and I went away along with him. When we reached the threshold of `Aisha's dwelling place, he thought that they had left, and so he returned and I too, returned along with him and found those people had left. Then the Prophet drew a curtain between me and him, and the Verses of Al-Hijab were revealed.

حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، قَالَ حَدَّثَنِي اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي أَنَسُ بْنُ مَالِكٍ ـ رضى الله عنه ـ أَنَّهُ كَانَ ابْنَ عَشْرِ سِنِينَ مَقْدَمَ رَسُولِ اللَّهِ صلى الله عليه وسلم الْمَدِينَةَ، فَكَانَ أُمَّهَاتِي يُوَاظِبْنَنِي عَلَى خِدْمَةِ النَّبِيِّ صلى الله عليه وسلم فَخَدَمْتُهُ عَشْرَ سِنِينَ، وَتُوُفِّيَ النَّبِيُّ صلى الله عليه وسلم وَأَنَا ابْنُ عِشْرِينَ سَنَةً، فَكُنْتُ أَعْلَمَ النَّاسِ بِشَأْنِ الْحِجَابِ حِينَ أُنْزِلَ، وَكَانَ أَوَّلَ مَا أُنْزِلَ 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 رَهْطٌ مِنْهُمْ عِنْدَ النَّبِيِّ صلى الله عليه وسلم فَأَطَالُوا الْمُكْثَ، فَقَامَ النَّبِيُّ صلى الله عليه وسلم فَخَرَجَ وَخَرَجْتُ مَعَهُ لِكَىْ يَخْرُجُوا، فَمَشَى النَّبِيُّ صلى الله عليه وسلم وَمَشَيْتُ، حَتَّى جَاءَ عَتَبَةَ حُجْرَةِ عَائِشَةَ، ثُمَّ ظَنَّ أَنَّهُمْ خَرَجُوا فَرَجَعَ وَرَجَعْتُ مَعَهُ، حَتَّى إِذَا دَخَلَ عَلَى زَيْنَبَ فَإِذَا هُمْ جُلُوسٌ لَمْ يَقُومُوا، فَرَجَعَ النَّبِيُّ صلى الله عليه وسلم وَرَجَعْتُ مَعَهُ، حَتَّى إِذَا بَلَغَ عَتَبَةَ حُجْرَةِ عَائِشَةَ، وَظَنَّ أَنَّهُمْ خَرَجُوا، فَرَجَعَ وَرَجَعْتُ مَعَهُ فَإِذَا هُمْ قَدْ خَرَجُوا فَضَرَبَ النَّبِيُّ صلى الله عليه وسلم بَيْنِي وَبَيْنَهُ بِالسِّتْرِ، وَأُنْزِلَ الْحِجَابُ‏.‏