The Baptism of the Lord is celebrated on the Sunday after Solemnity of the Epiphany, with which it is closely associated. We usually associate the Epiphany only with the coming of the Wise Men to Bethlehem. But Epiphany originally celebrated more than that. It is one of the oldest feasts in the Church, older than Christmas.
As it was originally observed in the Eastern Church, it celebrated many different epiphanies, or manifestations, of Christ to the world, including His Nativity. At His Birth, Christ was manifested as our Savior. The Angels said to the shepherds, "To you is born this day in the city of David, a Savior, who is Christ the Lord." (Lk 2:11) At His Baptism, He was manifested as God's Son by the Voice from heaven, "This is my beloved Son, with whom I am well pleased." (Mt 3:17) And at the Wedding at Cana, where He performed His first miracle, He manifested His power. Add to these the coming of the Wise Men, when Christ was manifested as our King to the Gentiles, and we have a whole series of epiphanies, all showing Christ in different ways, all celebrated originally in the one Feast of the Epiphany.
But it wasn't long before the Birth of Christ, being primary, was given a feast of its own. It was then, at least in the West, that the focus of Epiphany shifted to the coming of the Wise Men. And the other manifestations were celebrated later in the Season of Epiphany.
On the Sunday after Epiphany, we remember the next manifestation of our Lord after the coming of the Wise Men. After thirty years of quiet obscurity, in a small town in Galilee, He again showed Himself publicly. He came to John, at the River Jordan and was publicly baptized by him.
"In those days Jesus came from Nazareth of Galilee, and was baptized by John in the Jordan." (Mk 1:9) And there the Holy Spirit descended on Him, and the Father's Voice from heaven identified Him as His beloved Son, with whom He was well pleased.
The Baptism of Christ is not explained in Scripture. We know it is connected in some way with our own baptism, because John told the multitude, "I have baptized you with water; but he will baptize you with the Holy Spirit." (Mk 1:8) If John baptized with water only, Christ would baptize with the Holy Spirit. But if Christ Himself would baptize, with a baptism far greater than John's, why did He have to be baptized by John at all?
John's baptism was a sign of repentance, a symbolic act by which the person baptized renounced his sins. But John knew Jesus had no sins to renounce or repent of. And so he said, "I need to be baptized by you, and do you come to me?" (Mt 3:14) But Christ insisted. He said, "Thus it is fitting for us to fulfil all righteousness." (Mt 3:15) And so the question of why Christ had to be baptized can be put in these terms. How did Christ's being baptized fulfil all righteousness?
Baptism didn't begin with John the Baptist. It was originally a Jewish rite, which symbolized a washing from unrighteousness through the renunciation of sin. It was used until John's day for the cleansing of Gentiles who were converting to Judaism. John's baptism was revolutionary, in that he offered it to Jews -- meaning that they, no less than the Gentiles, needed to be cleansed of their sins. They were no better than the Gentiles in conforming their lives to the will of God. And this was a preparation for the teaching of Christ, that all mankind, Jew and Gentile alike, needs to come to Him for cleansing.
In light of all this, why was it necessary for Christ Himself to undergo a rite that symbolized repentance from sin? He had no sins to renounce or repent of. In being baptized, Christ renounced not His own sins, but the sins of mankind.
As John himself said, Jesus is the Lamb of God, who takes away the sins of the world. Our sins are taken away when God forgives us for them. And one condition for God to forgive us our sins is that we atone for them, or pay for them. Christ atoned for our sins by His death on the Cross. But there is another condition for our sins to be forgiven. We have to repent of them.
If we offend our neighbor, we can’t make it right if we're not sorry for offending him. Because if we're not sorry, the likelihood is that we'll do it again. If I stole money from you, I might try to atone for it by returning the money I stole. But would that make things right between us, if I didn't make it plain I intended never to steal from you again? Returning what I stole would be a form of making atonement. But in addition, I would have to repent of my sin -- be really sorry for it. Then you might forgive me. The same is true for our offenses against God. Being forgiven for our sins requires not only that we atone for them, but also that we repent of them.
Now consider that we can't really atone for our own sins. Nothing we do for God would be enough to pay for our sins against Him. We need a Savior to do it for us. In the same way, we can't fully repent of our sins against God. We're too immersed in our sins to be truly sorry for them. We need a Savior to do it for us. In order to be forgiven for our sins, we have not only to atone for our sins, but repent of them, and we can't do either except through our Savior.
Just as our Lord, though Himself sinless, would atone for our sins on Calvary, so He, even though sinless, repented of our sins in the Jordan River. In both cases, He acted not on His own behalf, but on behalf of all mankind. He represented us before God, at the beginning of His ministry, in His Baptism, just as He would represent us before God at the end of His ministry in His Crucifixion. In our place, He repented of our sins, just as in our place, He atoned for them.
When we are baptized, we are called upon, either personally, or through our sponsors, to renounce the world, the flesh, and the devil. In other words, we renounce sin in all its forms. Yet we could never renounce or repent of our sins apart from the repentance of Christ. There is nothing we can do, to free ourselves from sin and its consequences, except in and through Christ. What we do ourselves, apart from Christ, has no value at all for our salvation. But what we do with Christ, through Him, and in Him, has great value, because it shares in His holiness and perfection.
His Baptism was a great river of repentance, which flows over us when we are baptized. His repentance becomes our repentance, as we allow ourselves to be immersed in it. Then the Spirit of God descends on us, as He did on Christ. And the Father's Voice can be heard by the ear of faith, saying to us, as He did to Christ, "You are my beloved son with whom I am well pleased."