Musnad Ahmad 32:636

Hashim ibn al-Qasim narrated to us, he said: Jisr narrated to us, from Thabit, from Anas ibn Malik, who said: The Messenger of Allah, may Allah bless him and grant him peace, said: "Glad tidings to whoever believed in me and saw me," once. "And glad tidings to whoever believed in me and did not see me," seven times.