It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he said: Between Sayyiduna Adam and Sayyiduna Nuh (peace be upon them both) there was a span of ten generations, and all of them were upon a law of truth. Then, when differences arose among them, Allah Almighty sent the prophets and messengers and revealed His Book; before that they were a single nation. This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), and they did not record it.