Language:
كتاب النكاح
67  
Wedlock, Marriage (Nikaah)
(23)
Chapter: The milk belongs to the husband
(22)
باب لَبَنِ الْفَحْلِ
Sahih al-Bukhari 5103

Narrated Aisha:

that Aflah the brother of Abu Al-Qu'ais, her foster uncle, came, asking permission to enter upon her after the Verse of Al-Hijab (the use of veils by women) was revealed. `Aisha added: I did not allow him to enter, but when Allah's Messenger (ﷺ) came, I told him what I had done, and he ordered me to give him permission.

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ عَائِشَةَ، أَنَّ أَفْلَحَ، أَخَا أَبِي الْقُعَيْسِ جَاءَ يَسْتَأْذِنُ عَلَيْهَا ـ وَهْوَ عَمُّهَا مِنَ الرَّضَاعَةِ ـ بَعْدَ أَنْ نَزَلَ الْحِجَابُ، فَأَبَيْتُ أَنْ آذَنَ لَهُ، فَلَمَّا جَاءَ رَسُولُ اللَّهِ صلى الله عليه وسلم أَخْبَرْتُهُ بِالَّذِي صَنَعْتُ، فَأَمَرَنِي أَنْ آذَنَ لَهُ‏.‏
Reference : Sahih al-Bukhari 5103
In-book reference : Book 67, Hadith 41
USC-MSA web (English) reference : Vol. 7, Book 62, Hadith 40
  (deprecated numbering scheme)