Narrated Anas:

When the Prophet married Zainab, the people came and were offered a meal, and then they sat down (after finishing their meals) and started chatting. The Prophet showed as if he wanted to get up, but they did not get up. When he noticed that, he got up, and some of the people also got up and went away, while some others kept on sitting. When the Prophet returned to enter, he found the people still sitting, but then they got up and left. So I told the Prophet of their departure and he came and went in. I intended to go in but the Prophet put a screen between me and him, for Allah revealed:-- 'O you who believe! Enter not the Prophet's houses..' (33.53)

حَدَّثَنَا أَبُو النُّعْمَانِ، حَدَّثَنَا مُعْتَمِرٌ، قَالَ أَبِي حَدَّثَنَا أَبُو مِجْلَزٍ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ لَمَّا تَزَوَّجَ النَّبِيُّ ﷺ زَيْنَبَ دَخَلَ الْقَوْمُ فَطَعِمُوا، ثُمَّ جَلَسُوا يَتَحَدَّثُونَ فَأَخَذَ كَأَنَّهُ يَتَهَيَّأُ لِلْقِيَامِ فَلَمْ يَقُومُوا، فَلَمَّا رَأَى ذَلِكَ قَامَ، فَلَمَّا قَامَ قَامَ مَنْ قَامَ مِنَ الْقَوْمِ وَقَعَدَ بَقِيَّةُ الْقَوْمِ، وَإِنَّ النَّبِيَّ ﷺ جَاءَ لِيَدْخُلَ، فَإِذَا الْقَوْمُ جُلُوسٌ، ثُمَّ إِنَّهُمْ قَامُوا فَانْطَلَقُوا فَأَخْبَرْتُ النَّبِيَّ ﷺ فَجَاءَ حَتَّى دَخَلَ، فَذَهَبْتُ أَدْخُلُ فَأَلْقَى الْحِجَابَ بَيْنِي وَبَيْنَهُ، وَأَنْزَلَ اللَّهُ تَعَالَى {يَا أَيُّهَا الَّذِينَ آمَنُوا لاَ تَدْخُلُوا بُيُوتَ النَّبِيِّ} الآيَةَ. قَالَ أَبُو عَبْد اللَّهِ فِيهِ مِنْ الْفِقْهِ أَنَّهُ لَمْ يَسْتَأْذِنْهُمْ حِينَ قَامَ وَخَرَجَ وَفِيهِ أَنَّهُ تَهَيَّأَ لِلْقِيَامِ وَهُوَ يُرِيدُ أَنْ يَقُومُوا