Musnad Abu Ya'la al-Mawsili 155:350

Suwayd ibn Sa'id and a number [of others] narrated to us, they said: Marwan narrated to us, from Yazid ibn Kaysan, from Abu Hazim, from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, Islam began as a stranger, and it will return as a stranger just as it began, so glad tidings to the strangers."