Sahih al-Bukhari 5099

It is related from 'Amra bint 'Abdu'r-Rahman that 'A'isha, the wife of the Prophet, may Allah bless him and grant him peace, informed her that while the Messenger of Allah, may Allah bless him and grant him peace, was with her she heard the sound of a man asking permission to enter the house of Hafsa. 'A'isha said, "Messenger of Allah, this man is asking permission to enter your house." She said, "The Prophet, may Allah bless him and grant him peace, said, 'I think it is so-and-so,' the uncle of Hafsa by suckling." 'A'isha said, "If so-and-and (her uncle by suckling) has been alive, could he have visited me?" The Messenger of Allah, may Allah bless him and grant him peace, said, "Yes, suckling make unlawful what birth makes unlawful."