Matthew 3:13-17
Mat 3:13 (KJB)
Then cometh Jesus from Galilee to Jordan unto John, to be baptized of him.
Jesus had appeared in the temple at the age of twelve and nothing was heard about Him until now which was about eighteen years later. Jesus now appears to John at the Jordan river for the purpose of being baptized by him, symbolizing the baptism of death which He must undergo for all the Elect. A tremendous contrast between religion and true Christianity. The Pharisees and Sadducees had come to criticize what was going on and Jesus was there to begin His earthly ministry. (John 1:28 KJV) These things were done in Bethabara beyond Jordan, where John was baptizing.
Mat 3:14 (KJB)
But John forbad him, saying, I have need to be baptized of thee, and comest thou to me?
Since Johnís baptism was unto repentance for sin, John knew that Jesus did not have any sins to confess because here was the Son of God in the flesh. Just as Isaiah saw himself as being very sinful in the presence of a holy God, (Isa 6:5 KJV) Then said I, Woe is me! for I am undone; because I am a man of unclean lips, and I dwell in the midst of a people of unclean lips: for mine eyes have seen the King, the LORD of hosts. John also saw himself as sinful in the presence of the Son of God and needing to be baptized by Jesus for his sins.
Mat 3:15 (KJB)
And Jesus answering said unto him, Suffer it to be so now: for thus it becometh us to fulfil all righteousness. Then he suffered him.
At this point John did not know that Jesus was about to take upon Him all the sins of the Elect that He came to save and therefore he needed to be baptized by John. (2 Cor 5:21 KJV) For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him. Christ came to fulfill all the righteousness of the Father on behalf of all the Elect of God. Since Baptism was a part of the Christian life, Jesus needed to fulfill all the aspects of the Christian life because water baptism and the Lordís supper would be the two remembrances which would be commanded of Christians to keep. So John allowed Jesus to be baptized of him because all things in the earthly ministry of Jesus was planned and this was part of it.
Mat 3:16 (KJB)
And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him:
After Jesus had become baptized, he immediately went up out of the water and then the heavens being opened meant that a divine revelation was happening. The Lord Jesus then saw the Holy Spirit descend from Heaven and come upon Him. Notice that He descended like a dove. The dove represents a new era coming. Just as in Noahís time when he sent out the dove and came back with an olive leaf in its mouth. (Gen 8:11 KJV) And the dove came in to him in the evening; and, lo, in her mouth was an olive leaf plucked off: so Noah knew that the waters were abated from off the earth.  The end of judgment of the world was at hand and soon Noah and all the animals would be let go into a new world. Well the dove represents the coming of the kingdom of God and eternal salvation for all the Elect of God. The old ways of the Mosaic law will be over in three years as the Lord Jesus Christ will fulfill all the requirements of Godís Holy Law, resulting in salvation by grace.
Mat 3:17 (KJB)
And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
The voice from Heaven was God the Father. Verses 16 and 17 are killers to those who deny the trinity, especially the oneness Pentecostals and many cults. The entire Godhead was involved in this event. God speaks from Heaven that Jesus is His beloved Son in whom He is well pleased. This removes any doubt that Jesus was the Son of God and deity. This goes back to Isaiah 42. (Isa 42:1 KJV) Behold my servant, whom I uphold; mine elect, in whom my soul delighteth; I have put my spirit upon him: he shall bring forth judgment to the Gentiles. Here Jesus is referred to as His servant and His elect. We read that God has put His spirit upon Him as we read in verse 16 and the fact that He is going to bring judgment to the Gentiles, that is, He is going to die for the Elect, of whom many will be Gentiles from all over the world. God is now giving affirmation to the earthly ministry of His Son. The reason that the Christian can be pleasing to God is because we are in His Son, (Col 3:3 KJV) For ye are dead, and your life is hid with Christ in God. and since God was pleased with His Son, the sacrifice Christ made on Calvary was imputed to all the Elect and that is why the Christian, not the religious person pleases God.