Gregory the Great
Catena Aurea · Lukasevangelium 3
And he came into all the country about Jordan, preaching the baptism of repentance for the remission of sins; As it is written in the book of the words of Esaias the prophet, saying, The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight. Every valley shall be filled, and every mountain and hill shall be brought low; and the crooked shall be made straight, and the rough ways shall be made smooth; And all flesh shall see the salvation of God.
(ubi sup.) But the crooked places are become straight, when the hearts of the wicked, perverted by a course of injustice, are directed to the rule of justice. But the rough ways are changed to smooth, when fierce and savage dispositions by the influence of Divine grace return to gentleness and meckness.