The Baptism of the Lord (or the Baptism of Christ) is the feast day commemorating the baptism of Jesus in the Jordan River by John the Baptist. Originally the baptism of Christ was celebrated on Epiphany, which commemorates the coming of the Magi, the baptism of Christ, and the wedding at Cana. Over time in the West, however, the celebration of the baptism of the Lord came to be commemorated as a distinct feast from Epiphany.

Baptism of Christ fresco by Giotto di Bondone, c. 1305 (Cappella Scrovegni, Padua, Italy).
The Baptism of the Lord is observed as a distinct feast in the Roman Catholic Church, although it was originally one of three Gospel events marked by the feast of the Epiphany. Long after the visit of the Magi had in the West overshadowed the other elements commemorated in the Epiphany, Pope Pius XII instituted in 1955 a separate liturgical commemoration of the Baptism.
In fact, the Tridentine Calendar has no feast of the Baptism of the Lord. It was almost four centuries later that the feast was instituted, under the denomination "Commemoration of the Baptism of our Lord", for celebration on 13 January as a major double, using for the Office and the Mass those previously said on the Octave of the Epiphany, which Pius XII abolished; but if the Commemoration of the Baptism of Our Lord occurred on Sunday, the Office and Mass were to be those of the Feast of the Holy Family without any commemoration.
In his revision of the calendar five years later, Pope John XXIII kept on 13 January the "Commemoration of the Baptism of our Lord Jesus Christ", with the rank of a second-class feast.
In the Gospels of Matthew, Mark and Luke, the baptism of Jesus is recorded. In these three narratives, John is preaching repentance and baptizing at the Jordan for the forgiveness of sins. Jesus comes to John, who at first is reluctant to baptize Him. However, according to the passages written by Matthew, Jesus persuades John to do so “to fulfill all righteousness.”
John immerses Jesus and when He comes up out of the water, “the heavens were opened to Him, and He saw the Spirit of God descending like a dove and alighting upon Him. And suddenly a voice came from heaven, saying, 'This is My beloved Son, in whom I am well pleased.'” (Matthew 3:15-17) After this, Jesus goes into the wilderness and is tempted by the devil. Upon returning, Jesus begins His ministry.
In the Gospel of John, there is no mention of Jesus’ actual baptism. John the Baptist twice points out Jesus as “the Lamb of God.” Further, the gospel records that John bore witness, and said, “I saw the Spirit descending from heaven like a dove, and He remained upon Him. I did not know Him, but He who sent me to baptize with water said to me, ‘Upon whom you see the Spirit descending, and remaining on Him, this is He who baptizes with the Holy Spirit.” (John 1:32,33)
Only in the Gospel of John are these powerful words of John the Baptist recorded: “He who comes from above is above all; he who is of the earth is earthly and speaks of the earth. He who comes from heaven is above all. And what He has seen and heard, that He testifies; and no one receives His testimony. He who has received His testimony has certified that God is true. For He whom God has sent speaks the words of God, for God does not give the Spirit by measure. The Father loves the Son, and has given all things into His hand.” (John 3:31-35)
Reflection
In the life of Christ, His baptism in the Jordan is an event of the highest importance, because it represents a significant phase in the work of redemption. We know that the liturgy of the ecclesiastical year commemorates all the phases of Christ’s redemptive work; and recently, during the season of the Nativity, we have reflected on His coming into the world, poor and solitary in a grotto at Bethlehem, and on His circumcision. Now His baptism in the Jordan marks the divinely inaugurated beginning of Our Lord’s public life. Indeed, Saint Peter states that at His baptism, in fulfillment of the prophecy of Daniel, He was anointed by the Holy Spirit as the Christ, the Messiah, which means the Anointed One: “God anointed Jesus of Nazareth with the Holy Spirit and with power, and He went about doing good and healing all who were in the power of the devil, for God was with Him.” (Acts 10:38) An anointing has always been the symbolic, visible representation of an intimately established union, a specific, defined alliance or covenant between God and one of His servants. God the Father speaks at this moment, to make clear who this Person is. The foretold Saviour is His Divine Son, begotten from all eternity: “This is My Beloved Son, in whom I am well pleased.”
To sum up, today’s liturgy helps us to understand more clearly the basic structure of spiritual life, the redemptive acts of Christ. Upon that foundation the edifice rises through the Sacraments of Baptism and the Eucharist, while the Lord’s return, at our death, brings completion to the work.