Midrasz do Rodzaju 11:20

Ten generations there were from Noah to Abraham, to show how great is the clemency of God, for all the generations provoked His wrath, until Abraham our father came and received the reward of all of them. For the sake of Abraham God had shown himself long-suffering and patient during the lives of these ten generations. Yea, more, the world itself had been created for the sake of his merits. His advent had been made manifest to his ancestor Reu, who uttered the following prophecy at the birth of his son Serug: "From this child he shall be born in the fourth generation that shall set his dwelling over the highest, and he shall be called perfect and spotless, and shall be the father of nations, and his covenant shall not be dissolved, and his seed shall be multiplied forever."