Maliks Muwatta Book 030, Hadith Number 001.

Section : Suckling of the Young.

Yahya related to me from Malik from Abdullah ibn Abi Bakr from Amra bint Abd ar-Rahman that A'isha, umm al-muminin informed her that the Messenger of Allah, may Allah bless him and grant him peace, was with her and she heard the voice of a man asking permission to enter the room of Hafsa. A'isha said that she had said, "Messenger of Allah! There is a man asking permission to enter your house!" The Messenger of Allah, may Allah bless him and grant him peace, said, "I think it is so-and-so" (referring to a paternal uncle of Hafsa by suckling). A'isha said, "Messenger of Allah! If so-and-so were alive (referring to her paternal uncle by suckling) could he enter where I am?" The Messenger of Allah, may Allah bless him and grant him peace, said, "Yes. Suckling makes haram as birth makes haram."