Abu Dawud
Model Behavior Of The Prophet (PBUH)
Book Number: 035 / Hadith Number: 4579
Narated By AbuHurayrah : The Prophet (pbuh) said: The Jews were split up into seventy-one or seventy-two sects; and the Christians were split up into seventy one or seventy-two sects; and my community will be split up into seventy-three sects.