Full Sharh — Sahih Muslim 3579
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، ح وَحَدَّثَنَا مُحَمَّدُ بْنُ رُمْحٍ، أَخْبَرَنَا اللَّيْثُ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ عِرَاكٍ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، أَنَّهَا أَخْبَرَتْهُ أَنَّ عَمَّهَا مِنَ الرَّضَاعَةِ - يُسَمَّى أَفْلَحَ - اسْتَأْذَنَ عَلَيْهَا فَحَجَبَتْهُ فَأَخْبَرَتْ رَسُولَ اللَّهِ صلى الله عليه وسلم فَقَالَ لَهَا " لاَ تَحْتَجِبِي مِنْهُ فَإِنَّهُ يَحْرُمُ مِنَ الرَّضَاعَةِ مَا يَحْرُمُ مِنَ النَّسَبِ " .
English Translation
A'isha (Allah be pleased with her) reported that her foster-uncle whose name was Aflah sought permission from her (to enter the house) but she observed seclusion from him, and informed Allah's Messenger (ﷺ) who said to her:Don't observe veil from him for he is Mahram (one with whom marriage cannot be contracted) on account of fosterage as one is Mahram on account of consanguinity
Source
Sahih Muslim(صحيح مسلم)
The Book of Suckling
Hadith Number
3579