Narrated Aisha (Radi-Allahu 'anha)

Narrated Aisha (Radi-Allahu 'anha):

Once the Prophet (Sallallahu 'Alaihi Wa Sallam) 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)."

Bukhari Vol. 3 : No. 815