8 Nor did these calls to penance cease when the Son of God became incarnate. On the contrary, they became even more insistent. At the very outset of his preaching, John the Baptist proclaimed: "Do penance, for the kingdom of heaven is at hand."(7) And Jesus inaugurated His saving mission in the same way. He did not begin by revealing the principal truths of the faith. First He insisted that the soul must repent of every trace of sin that could render it impervious to the message of eternal salvation: "From that time Jesus began to preach and to say, Do penance, for the kingdom of heaven is at hand."(8)
Source: Paenitentiam Agere (Vatican.va)