Jesus was without sin! Why was Jesus Baptised? I The Purpose and Significance of Baptism of Jesus.

John’s Baptism was a baptism of repentance, for the remission of sins.
Why was Jesus baptized at the hands of a man who preached a baptism for the forgiveness of sins?
Jesus was without sin. Why was Jesus baptized?
Did He need baptism? Why did He have to receive the Holy Spirit?
Isn’t the Son, one with the Spirit
Jesus, Himself did not need baptism, however in being baptized our Lord accomplished and fulfilled many things.

1. The Son of God was revealed to the world. “I have seen and I testify that this is God’s Chosen One” (Jn. 1: 34). He is revealed to us all, as the Son of God, on this day. “You are My Son, whom I love; with you I am well pleased.” He is revealed by the Father and the Holy Spirit, as the Son of God. The time had come to reveal the Gospel through His Life, Death, Resurrection, Ascension and Glorification beginning first with His baptism. However, Jesus does not become Son of God on this day, as the Holy Spirit has always rested on Him.
2. The Great Mystery of Holy Trinity was revealed for the first time, in Fullness. There were many shadows of Holy Trinity earlier in the Old Testament. Incarnate Son, Jesus is baptized; the Father speaks (Voice); and the Holy Spirit descends (Dove). In the Old Testament times, God was only identified or revealed as Trinity, indirectly. It was at the time of baptism of Jesus in River Jordan, the Holy Trinity was revealed to the world explicitly and vividly. This is the importance of Epiphany. 
3. Baptism of Jesus’ was an Anointment of Christ, by the Father with the Holy Spirit. In the Old Testament, prophets, priests, and kings were always anointed in some way to signify that they were chosen of God (Exodus 28: 41; 29: 7; I Kings 19: 16). The oil used was symbolic of the Holy Ghost. Jesus was anointed by the Spirit of God Himself, instead of being anointed with oil that was symbolic of the Holy Ghost, signifying that He came to fulfill the roles of prophet, priest, and king (Psalm 45: 7-8; Isaiah 61: 1).
4. To reveal Jesus to Israel (Jn. 1: 31). God has been gradually revealing Himself to the universe for ages through His prophets and high priests (Heb. 1: 1). But all these were only partial and His complete revelation came through Jesus Christ, His Son. Son is the complete manifestation of God the Father, the radiance of His glory and exact representation of His being (Heb. 1: 3). St John the Baptist, was the witness ‘Behold the Lamb of God, that takes Who takes away the sin of the world’ (Jn. 1: 29)
5. He opened the Heaven to a World, that separated from God through sin. In the opening of heaven reconciliation between Creator and creation through the Redeemer by the testimony of the Holy Spirit took place. The dove signaled to Noah that the God’s wrath against man had ceased. Here the Holy Spirit announces that Christ has reconciled us to God by cleansing the sin away in the waters of baptism. The heaven and earth respected and yielded to the Creator. The Logos, Himself did not need to be baptized or receive the Spirit, but He did it for our human nature, so that through Christ’s baptism, our human nature is renewed by the washing away of sins.
6. To Fulfill all Righteousness (Matt. 3: 15). The words for righteous in both Hebrew and Greek mean “doing what God requires; responding to the revealed will of God.” Righteousness is what results when God or human beings fulfill the conditions imposed upon them by a relationship. All of this lies behind Jesus’ response to John. He was informing John that the baptism would play a role in the accomplishment of the Holy Father’s will.  All God’s righteous requirements were fully met in Christ. Jesus is responding to the revealed will of God, participating in God’s righteous work of saving God’s people.
7. He Revealed His Messiahship (Jn. 1: 41). The only purpose of John’s baptism was to publicly testify Jesus as Christ, the anointed, before commencement of public ministry. He came to bear witness to light, Jn. 1: 8. “I did not know him, but that he should be revealed to Israel, therefore I came baptizing with water” Jn. 1:31. 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. I have seen and testified that this is the Son of God,” Jn. 1: 33-34. The baptism of Jesus fulfills the need as the Messiah is identified to John the Baptist, by a special Theophany of the Holy Spirit.
8. To carry out the Succession and Culmination of Old Testament. Aaronic priesthood, which John the Baptist had inherited through his father priest Zachariah to Jesus Christ. According to Levites the transfer of priest hood can be done only after the age of 30. This authority to renew others is given only to the apostles that have now received the Grace of Christ’s Priesthood Remember the hymn we sing in the kukillion commemorating the departed clergy. ……. Skariah gave this authority to John and John gave it to his disciples. They in turn passed it throughout the world……..
9. The Baptism of Jesus marks the inauguration of Jesus’ earthly redemptive ministry, as well as the decline and decrease of John the Baptist’s ministry.
10. Jesus is revealed as God’s ‘Beloved One’. Many titles have been given to Jesus: Son of David, Son of God, Messiah, Savior of the world; but now, He is revealed as the Beloved One of God the Father.
11. He entered the waters, sanctifying and hallowing the water itself. During the service on Denaha (and in the Sacrament of Holy Baptism) in Orthodox Churches, there is the sanctifying of waters by invocation of the Holy Spirit that appeared in the form of a dove over Christ at the time of His Baptism. The believers receive sanctified water at the end of the special service of Epiphany and with it sanctify the homes of the faithful. While some preserve it for the entire year partaking of it at times of illness and other personal or family adversities. When He stepped into the water of Jordan, the entire creation was blessed and sanctified, where as in our baptism, our sins are washed away. This renewal includes forgiveness of sins and unity with God through the indwelling of the Holy Spirit.
12. Jesus Christ was washed in the River Jordan. The Jewish Law, stated that the sacrificial offerings must be washed, before sacrifice. Jesus gave Himself up as a sacrificial offering on Mount Calvary.
13. Jesus’ baptism symbolized our sins, He would wash away and bury with Himself. Since water baptism is the symbolic act of washing away and burying of sin. St. Gregory of Nazianzus says that by entering into the waters of Jordan God purified the whole element of water, which suffered defilement by the fall of man, thus reverting to the original status.
14. In baptism we are promised that same Spirit which descended upon Jesus in the form of a dove – God’s Spirit.
15. He identified with His people by descending into the waters, with them.
16. The raising of Jesus from the waters of Jordan, heaven’s opening, the Spirit descending and the Father’s voice from heaven symbolized His coming, Resurrection, Ascension and Glorification.
17. Tradition says that when Lord Jesus stepped in the Jordan water, darkness was drawn back and brightness came over the water. Thus, the light of the world, our Lord came to the world to eradicate the darkness of all types.  

The Baptism of Jesus was a very public one and was recorded for all generations to know about and understand.