"MiPnei May HaMabul" (Perek Zayin, Pasuk Zayin). The Pasuk tells us that Noach, his sons, his wife and his son's wives entered the tevah before the waters came. Why does the Torah find it necessary to tell us something so obvious, of course they went into the tevah before the waters came. Rashi explains that Noach was from "Kutnei Emunah", people of little faith. He didn’t believe the Mabul would come until the water actually came to his knees. This Rashi is difficult to understand. Noach was a Gadol, a leader of his generation, how can it be that he had very little faith. He wasn’t a man of little faith. If you read the words of Rashi just a little differently the meaning is completely different. "Af Noach B’kutnei Emunah Haya Mamin ", Noach believed in those people who had very little faith. He believed they would do Teshuva. "V’eino Mamin Shyavo HaMabul" and he didn’t believe the Mabul would come. Hashem had already said that if they did Teshuva the waters would become "Mayim Shel Bracha", water of Bracha. That is why Noach did not go into the tevah until the waters came, because he was waiting for the people of his generation to do Teshuva.