Amrah bint Abd al-Rahman said that Sayyidah Aishah (may Allah be pleased with her) informed her that one day the Messenger of Allah (peace and blessings be upon him) was with her when Sayyidah Aishah (may Allah be pleased with her) heard the voice of a man asking permission to enter the house of Sayyidah Hafsah (may Allah be pleased with her). Sayyidah Aishah (may Allah be pleased with her) said: O Messenger of Allah, this man is asking permission to enter your house. She said that the Messenger of Allah (peace and blessings be upon him) said: "He is Hafsah's paternal uncle through nursing." Sayyidah Aishah (may Allah be pleased with her) said: If so-and-so, who was her paternal uncle through nursing, were alive, could he enter my house? He (peace and blessings be upon him) said: "Yes, because nursing also makes forbidden those relations that lineage does."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13902