Musnad Abu Ya'la al-Mawsili 117:117

Al-Fadl ibn al-Sabah narrated to us, Abu Ubaydah narrated to us, from Muhtasib, from Thabit, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Glad tidings to whoever saw me and believed in me once, and glad tidings to whoever did not see me and believed in me seven times."