Halakhah for Sanhedrin 195:19

And, in truth, not against Him (G–d forbid) is our plaint, but against ourselves; for it [the redemption] is not beyond His powers, viz. (Isaiah 59:1-2): "Behold, the L–rd's hand is not too short to save, and His ear is not too heavy to hear. But your sins have made a separation between you and your G–d, and your transgressions have hid [His] face from you, from hearing." And we find (viz. Sanhedrin 98a) that in the days of R. Yehoshua ben Levi he was told (viz. Tehillim 95:6) that the Messiah would come "today, if you hearkened to His voice" — even though the time of the exile decreed for Israel (one thousand years, corresponding to the one thousand year "day" of the Holy One Blessed be He, had not yet passed [viz. Chida, Petach Eiynayim, Sanhedrin, Ibid.]) In spite of this, the power of repentance would have annulled the decree. How much more so, more than eight hundred years after the end of that [one-thousand-year] "day", [should the Messiah come if we repented]! The fault is ours alone — that with our many sins we do not allow Him to repose His Shechinah in our midst.