Musnad Ahmad 1153:1772

Waki’ narrated to us, from Sufyan, and ‘Abd al-Rahman, from Sufyan, from Ash’ath, from his father, from Masruq, from ‘Aisha, that the Prophet (peace be upon him) entered upon ‘Aisha while a man was with her. He said: "Who is this?" She said: "My foster brother." The Prophet (peace be upon him) said: "Look into who your foster relatives are, for indeed, fosterage is only from hunger." ‘Abd al-Rahman said: "Look into who your brothers are, for indeed, fosterage is only from hunger."