Sahih Muslim 1445 c
The Book of Suckling
The prohibition that results from breastfeeding is related to the issue of the male
'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 (ﷺ) 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 (ﷺ) entered, I said: Allah's Messenger (ﷺ) , 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 Messenger (ﷺ) 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.