(7) باب الشَّهَادَةِ عَلَى الأَنْسَابِ وَالرَّضَاعِ الْمُسْتَفِيضِ وَالْمَوْتِ الْقَدِيمِ
Narrated Aisha:
Once the Prophet (ﷺ) 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).
Reference: Sahih al-Bukhari 2647
In-book reference: Book 52, Hadith 11
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 48, Hadith 815