The Creator tells Noah that the world is going to be destroyed, and so He wants him to take 120 years to build a teyvat, an Ark, through which he and his family will be saved.
A question we should ask is, why 120 years? The Midrash answers: because the Creator wanted, through those 120 years, as Noah is chopping down the trees and building the Ark, all the people of the generation to ask him why he was building an ark. To which Noah would respond, “Because the Creator told me that the path humanity is on right now is a path of destruction, and if we continue on this path we are going to bring destruction to the entire world and to ourselves. That’s why I’m building the Ark, because if that destruction happens, at least my family and I can be saved.”
All the people of the generation laughed at him, telling him that if a flood did come, it would go on the house of Methushelach, a great... read more