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.) Or else, All flesh, i. e. Every man can not see the salvation of God in Christ in this life. The Prophet therefore stretches his eye beyond to the last day of judgment, when all men both the elect and the reprobate shall equally see Him.