A Reading from the Holy Gospel according to Luke
Now in the fifteenth year of the reign of Tiberius Caesar, Pontius Pilate being governor of Judaea, and Herod being tetrarch of Galilee, and his brother Philip tetrarch of Ituraea and of the region of Trachonitis, and Lysanias the tetrarch of Abilene, Annas and Caiaphas being the high priests, the word of God came unto John the son of Zacharias in the wilderness. 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.
A Homily of Pope Saint Gregory
The names of the reigning sovereign of the Roman empire and of the kings of Judea serve to indicate the period when the Forerunner of our Redeemer took up his task of preaching. John had come to announce Him who would redeem some of the Jews and many of the Gentiles. Hence the span of his preaching is designated by mentioning who it was who ruled the Gentiles at that time and who they were who governed the Jews. The very manner of enumerating these earthly rulers suggests that the Gentiles would be gathered together, but the Jews scattered because of their sin of unbelief. For it is shown that in the Roman republic one man was in charge, while in the Judean kingdom the authority was split four ways.
Indeed, we have it from the mouth of our Redeemer that "every kingdom divided against itself is brought to desolation." It becomes clear, then, that a Judea split under so many rulers had reached its end as a kingdom. And not only the civil rulers are mentioned, but also the high priests who were in office when these things took place. And rightly so; for John the Baptist was announcing One Who was King and Priest at the same time. Hence the Evangelist Luke fixes the period of John's preaching by reference to both kingdom and priesthood.
"And he went into all the region about the Jordon, preaching a baptism of repentance for the forgiveness of sins." It is clear to any reader that John not only preached a baptism of repentance, but also administered it to some. Yet his baptism was not able to effect the remission of sins. It is only in Christ's baptism that our sins are remitted. We must pay attention to the wording, therefore: "preaching a baptism of repentance for the forgiveness of sins." John could not give a baptism which would remit sins, and so he preached that kind of baptism. Observe the parallel: just as John by the "word" of his preaching was the forerunner of the incarnate Word of the Father, so by his baptism, which could not remit sins, he was forerunner of the baptism of repentance by which sins are remitted.