صحيح البخاري Sahih Bukhari كتاب الاستئذان The Book of Asking Permission
بَابُ التَّسْلِيمِ وَالاِسْتِئْذَانِ ثَلاَثًا:

(13) Chapter. To greet somebody and ask permission thrice (only).

2 hadith
Hadith 6244
حَدَّثَنَا إِسْحَاقُ ، أَخْبَرَنَا عَبْدُ الصَّمَدِ ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ الْمُثَنَّى ، حَدَّثَنَا ثُمَامَةُ بْنُ عَبْدِ اللَّهِ ، عَنْ أَنَسٍ رَضِيَ اللَّهُ عَنْهُ ، أَنّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ " إِذَا سَلَّمَ سَلَّمَ ثَلَاثًا ، وَإِذَا تَكَلَّمَ بِكَلِمَةٍ أَعَادَهَا ثَلَاثًا " .
Narrated Anas: Whenever Allah's Apostle greeted somebody, he used to greet him three times, and if he spoke a sentence, he used to repeat it thrice.
Hadith Reference Sahih Bukhari / The Book of Asking Permission / Hadith: 6244
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة
Hadith 6245
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ ، حَدَّثَنَا سُفْيَانُ ، حَدَّثَنَا يَزِيدُ بْنُ خُصَيْفَةَ ، عَنْ بُسْرِ بْنِ سَعِيدٍ ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ ، قَالَ : كُنْتُ فِي مَجْلِسٍ مِنْ مَجَالِسِ الْأَنْصَارِ ، إِذْ جَاءَ أَبُو مُوسَى كَأَنَّهُ مَذْعُورٌ ، فَقَالَ : اسْتَأْذَنْتُ عَلَى عُمَرَ ثَلَاثًا ، فَلَمْ يُؤْذَنْ لِي ، فَرَجَعْتُ ، فَقَالَ : مَا مَنَعَكَ ؟ قُلْتُ : اسْتَأْذَنْتُ ثَلَاثًا ، فَلَمْ يُؤْذَنْ لِي ، فَرَجَعْتُ ، وَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " إِذَا اسْتَأْذَنَ أَحَدُكُمْ ثَلَاثًا ، فَلَمْ يُؤْذَنْ لَهُ ، فَلْيَرْجِعْ " ، فَقَالَ : وَاللَّهِ لَتُقِيمَنَّ عَلَيْهِ بِبَيِّنَةٍ أَمِنْكُمْ أَحَدٌ سَمِعَهُ مِنَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، فَقَالَ أُبَيُّ بْنُ كَعْبٍ : وَاللَّهِ لَا يَقُومُ مَعَكَ ، إِلَّا أَصْغَرُ الْقَوْمِ ، فَكُنْتُ أَصْغَرَ الْقَوْمِ ، فَقُمْتُ مَعَهُ ، فَأَخْبَرْتُ عُمَرَ : أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ ذَلِكَ ، وَقَالَ ابْنُ الْمُبَارَكِ ، أَخْبَرَنِي ابْنُ عُيَيْنَةَ ، حَدَّثَنِي يَزِيدُ بْنُ خُصَيْفَةَ ، عَنْ بُسْرِ بْنِ سَعِيدٍ ، سَمِعْتُ أَبَا سَعِيدٍ ، بِهَذَا .
Narrated Abu Sa`id Al-Khudri: While I was present in one of the gatherings of the Ansar, Abu Musa came as if he was scared, and said, "I asked permission to enter upon `Umar three times, but I was not given the permission, so I returned." (When `Umar came to know about it) he said to Abu Musa, "Why did you not enter?'. Abu Musa replied, "I asked permission three times, and I was not given it, so I returned, for Allah's Apostle said, "If anyone of you asks the permission to enter thrice, and the permission is not given, then he should return.' " `Umar said, "By Allah! We will ask Abu Musa to bring witnesses for it." (Abu Musa went to a gathering of the Ansar and said). "Did anyone of you hear this from the Prophet ?" Ubai bin Ka`b said, "By Allah, none will go with you but the youngest of the people (as a witness)." (Abu Sa`id) was the youngest of them, so I went with Abu Musa and informed `Umar that the Prophet had said so. (See Hadith No. 277, Vol. 3)
Hadith Reference Sahih Bukhari / The Book of Asking Permission / Hadith: 6245
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة