Narrated Aisha: Once the Prophet came to me while a man was in my house. He said, "O `Aisha! Who is this (man)?" I replied, "My foster brothers" He said, "O `Aisha! Be sure about your foster brothers, as fostership is only valid if it takes place in the suckling period (before two years of age).

Narrated `Aisha: that the Prophet entered upon her while a man was sitting with her. Signs of answer seemed to appear on his face as if he disliked that. She said, "Here is my (foster) brother." He said, "Be sure as to who is your foster brother, for foster suckling relationship is established only when milk is the only food of the child."