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Surah 24. An-Nur
Ayah 62
62 إِنَّمَا ٱلْمُؤْمِنُونَ ٱلَّذِينَ ءَامَنُوا۟ بِٱللَّهِ وَرَسُولِهِۦ وَإِذَا كَانُوا۟ مَعَهُۥ عَلَىٰٓ أَمْرٍ جَامِعٍ لَّمْ يَذْهَبُوا۟ حَتَّىٰ يَسْتَـْٔذِنُوهُ ۚ إِنَّ ٱلَّذِينَ يَسْتَـْٔذِنُونَكَ أُو۟لَـٰٓئِكَ ٱلَّذِينَ يُؤْمِنُونَ بِٱللَّهِ وَرَسُولِهِۦ ۚ فَإِذَا ٱسْتَـْٔذَنُوكَ لِبَعْضِ شَأْنِهِمْ فَأْذَن لِّمَن شِئْتَ مِنْهُمْ وَٱسْتَغْفِرْ لَهُمُ ٱللَّهَ ۚ إِنَّ ٱللَّهَ غَفُورٌ رَّحِيمٌ
62. The believers are only those who believe in Allah and His Messenger; and when they are with him on some common matter, they go not away until they have asked his permission. Verily, those who ask your permission, those are they who (really) believe in Allah and His Messenger. So if they ask your permission for some affairs of theirs, give permission to whom you will of them, and ask Allah for their forgiveness. Truly, Allah is Oft-Forgiving, Most Merciful.
This is another matter of etiquette to which Allah has guided His believing servants. Just as He commanded them to seek permission when entering, He also commanded them to seek permission when leaving, especially when they are doing something together with the Messenger , such as the Friday, `Id, or congregational prayers, or a meeting for the purpose of consultation and so on. Allah commanded them not to leave him in these situations until they had asked his permission. If they did this, then they were of the true believers. Then Allah commanded His Messenger to give permission when someone asked for it, if he wanted to. He said:
(give permission to whom you will of them, and ask Allah for their forgiveness.)Abu Dawud reported that Abu Hurayrah said, "The Messenger of Allah said:
(When any of you joins a gathering, let him say Salam, and when he wants to leave, let him say Salam. The former is not more important than the latter.) This was also recorded by At-Tirmidhi and An-Nasa'i; At-Tirmidhi said: "It is a Hasan Hadith.''