(4) باب مَا جَاءَ فِي بُيُوتِ أَزْوَاجِ النَّبِيِّ صلى الله عليه وسلم، وَمَا نُسِبَ مِنَ الْبُيُوتِ إِلَيْهِنَّ
Narrated `Amra bint `Abdur-Rahman:
`Aisha, the wife of the Prophet (ﷺ) told her that once Allah's Messenger (ﷺ) was with her and she heard somebody asking permission to enter Hafsa's house. She said, "O Allah's Messenger (ﷺ)! This man is asking permission to enter your house." Allah's Messenger (ﷺ) replied, "I think he is so-and-so (meaning the foster uncle of Hafsa). What is rendered illegal because of blood relations, is also rendered illegal because of the corresponding foster-relations."
Reference: Sahih al-Bukhari 3105
In-book reference: Book 57, Hadith 14
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 4, Book 53, Hadith 337