Mishnà su Genesi 15:3

He used to say: the father transmits to the son beauty, strength, wealth, wisdom and years. And the number of generations before Him, that shall be their appointed end: For it is said, “calling the generations from the beginning” (Isaiah 41:4) Although it is said, “And shall serve them, and they shall afflict them four hundred years” (Genesis 15:13), it is also said, “And in the fourth generation they shall come hither again” (Genesis 15:16).