Q 96: When did the differing take place?
A--- Ibn "Abbas (May Allah be pleased with them) said: Between Nuh (Noah) and Adam were 10 centuries of true and pure Tawhid (Islamic Monotheism) till they (the people) differed. {And Allah sent Prophets with glad tidings and warnings}. (Al-Baqarah, 213)
Reference: 200 FAQ On Muslims Belief - Shiekh Hafiz Ibn Ahmed Al Hakami