מדרש אויף דברים 4:1

Thy right hand, O Lord (Exod. 15:6). This verse indicates that the Lord’s right hand is stretched out to receive repentant sinners. Though You set a time for the generation of the flood in which to do penance, as it is said: My spirit shall not abide in man forever (Gen. 6:3), You did not decree their destruction until they committed their most evil acts before You. Similarly, You set a time limit in which the men of the Tower of Babel were to repent, yet You did not decree their extinction until they performed their most wicked acts, as it is said: And now nothing will be withholden from them (ibid. 11:6). The expression and now is employed only to signify that they had an opportunity to repent, as is said: And now, Israel, what doth the Lord thy God require of thee? (Deut. 10:12); And now, O Israel, hearken unto the statutes (ibid. 4:1); And yet now hear, O Jacob (Isa. 44:1).

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!