Urwah (may Allah have mercy on him) said: Sayyidah Aishah (may Allah be pleased with her) informed me that her uncle, the brother of Abu al-Qu'ays, came and asked permission to come in to her after the command of hijab had been revealed. Sayyidah Aishah (may Allah be pleased with her) refused to give him permission until the Messenger of Allah (peace and blessings be upon him) came and she could ask his permission. When the Messenger of Allah (peace and blessings be upon him) came, she mentioned this to him (peace and blessings be upon him): My uncle, the brother of Abu al-Qu'ays, came, and I sent him back until I could ask your (peace and blessings be upon him) permission. He (peace and blessings be upon him) said: "Is he not your uncle?" I said: It was the woman who suckled me; the man did not suckle me. He (peace and blessings be upon him) said: "He is your uncle; he may come in to you." Sayyidah Aishah (may Allah be pleased with her) used to treat as unlawful through suckling (the relations) that are unlawful through birth.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15609