Sahih Muslim , Book 17, Hadith 6 (In-Book) ⓘ

'A'isha (Allah be pleased with her) reported that there came Aflah the brother, of Abu'l-Qu'ais, who sought her permission (to enter) after seclusion was instituted, and AbuQu'ais was the father of 'A'isha by reason of fosterage. 'A'isha said: By Allah, I would not permit Aflah unless I have solicited the opinion of Allah's Messenger for Abu Qulais has not suckled me, but his wife has given me suck. 'A'isha' (Allah be pleased with her) said: When Allah's Messenger entered, I said: Allah's Messenger, Aflah is the brother of Abu'l-Qulais; he came to me to seek my permission for entering (the houst). I did not like the idea of granting him permission until I had solicited your opinion. Thereupon Allah's Apostle said: Grant him permission. 'Urwa said it was on account of this that 'A'isha used to say. What is unlawful by reason of consanguinity is unlawful by reason of fosterage.

وَحَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ، أَنَّ عَائِشَةَ، أَخْبَرَتْهُ أَنَّهُ، جَاءَ أَفْلَحُ أَخُو أَبِي الْقُعَيْسِ يَسْتَأْذِنُ عَلَيْهَا بَعْدَ مَا نَزَلَ الْحِجَابُ - وَكَانَ أَبُو الْقُعَيْسِ أَبَا عَائِشَةَ مِنَ الرَّضَاعَةِ - قَالَتْ عَائِشَةُ فَقُلْتُ وَاللَّهِ لاَ آذَنُ لأَفْلَحَ حَتَّى أَسْتَأْذِنَ رَسُولَ اللَّهِ صلى الله عليه وسلم فَإِنَّ أَبَا الْقُعَيْسِ لَيْسَ هُوَ أَرْضَعَنِي وَلَكِنْ أَرْضَعَتْنِي امْرَأَتُهُ - قَالَتْ عَائِشَةُ - فَلَمَّا دَخَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم قُلْتُ يَا رَسُولَ اللَّهِ إِنَّ أَفْلَحَ أَخَا أَبِي الْقُعَيْسِ جَاءَنِي يَسْتَأْذِنُ عَلَىَّ فَكَرِهْتُ أَنْ آذَنَ لَهُ حَتَّى أَسْتَأْذِنَكَ - قَالَتْ - فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ ائْذَنِي لَهُ ‏" ‏ ‏.‏ قَالَ عُرْوَةُ فَبِذَلِكَ كَانَتْ عَائِشَةُ تَقُولُ حَرِّمُوا مِنَ الرَّضَاعَةِ مَا تُحَرِّمُونَ مِنَ النَّسَبِ ‏.‏