Midrasch zu Tehillim 95:10

R. Simlai lectured: "What does the passage (Am. 5, 18) Woe unto you that long for the day of the Lord, mean? For what do you wish the day of the Lord? It is [one of] darkness and not of light. This might be likened unto a cock and a bat, which were waiting for daybreak. The cock said to the bat, 'I look out for the light, because the light is mine (I see it), but for what purpose do you wait for it?'" Ib. 33) And this is what a Sadducee said to R. Abahu: "When will your Messiah appear?" And he answered: "When your people will be surrounded with darkness." "Art thou trying to curse me?" asked the Sadducee. He answered: "No, it is written so (Isa. 60, 2) For behold, the darkness shall cover the earth, and a gross darkness the people; but over thee will shine forth the Lord, and His glory will be seen over thee?" We are taught in a Baraitha that R. Elazar says: "Forty years will be the Messianic period, as it is said (Ps. 95, 10) Forty years did I feel loathing on this generation." R. Elazar b. Azaryah says: "Seventy years, as it is said (Is. 23, 15) And it shall come to pass on that day that Tyre shall be forgotten for seventy years, like the days of one king; i.e., who is meant by the one king? The Messiah is meant." Rabbi, however, says: "It will continue for three generations," as it is said (Ps. 72, 5) They shall fear thee, as long as the sun shineth, and in the presence of the moon throughout all generations." R. Hillel, however, says: "Israel has no more Messiah to expect, for they have already enjoyed him in the days of Hezekiah." R. Joseph said: "May the Lord forgive R. Hillel [for his statement] for Hezekiah was there at the time of the first Temple, and Zacharyah, who prophesied at the time of the second Temple, said (Zech. 9, 9) Be exceedingly glad, O daughter of Zion; shout, O daughter of Jerusalem! Behold, thy king will come unto thee, righteous and victorious, lowly, and riding upon an ass, and upon a call the foal of a she-ass."

Variantly: He (Moses) said to them: "And we abode in the valley opposite Beth Peor." See the difference between you and me. How many prayers did I pray? Yet it was decreed upon me not to enter the land. But you angered Him for forty years, as it is written (Psalms 95:10) "Forty years I was angry with the generation. And, what is more, the greatest among you prostrated themselves to Peor, yet His right hand is stretched forward to accept penitents, so (Devarim 4:1) "now, O Israel, hearken to the statutes" — You are new; the past has been forgiven!