Variantly: "from generation to generation": R. Yehoshua says: "from generation" — the life of this world: "to generation" — the life of the world to come. R. Eliezer Hamodai says: from the generation of Moses and from the generation of Samuel, (who commanded that revenge be taken of Amalek.) R. Eliezer says: "from the generation of the Messiah" — two generations. And whence is it derived that the generation of the Messiah is two generations? From (Psalms 72:5) "They will fear You (in the time of the Messiah) with the sun and before the moon, generation, generations."