Musnad Ahmad 32:637

Hashim ibn al-Qasim narrated to us, Jisr narrated to us, from Thabit, from Anas ibn Malik, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I wish I had met my brothers." He said: The companions of the Prophet (peace and blessings of Allah be upon him) said: "Are we not your brothers?" He said: "You are my companions, but my brothers are those who believed in me and did not see me."