Musnad Ahmad 1153:1425

He said: I read to Abd al-Rahman: Malik, from Ibn Shihab, from Urwah, from Aisha, that she informed him that Aflah, the brother of Abu al-Qu'ays, came seeking permission to enter upon her—and he was her paternal uncle through breastfeeding—after the hijab had been revealed. She said: So I refused to give him permission. When the Prophet, peace and blessings of Allah be upon him, came, I informed him of what I had done. He commanded me to give him permission to enter upon me.