Matthew 3:15 records the baptism of Jesus:
“Then Jesus arrived from Galilee at the Jordan coming to John, to be baptized by him. But John tried to prevent Him. Saying, ‘I have need to be baptized by You, and do You come to me?”

So, who is this John recorded in writings by Matthew?

In the Old Testament, about 700 years before Christ’s birth, the prophet Isaiah spoke of one coming before the Messiah.
“Clear the way for the Lord in the wilderness; make smooth in the desert a highway for our God. Let every valley be lifted up, and every mountain and hill be made low; and let the rough ground become a plain, and the rugged terrain a broad valley; then the glory of the Lord will be revealed, and all flesh will see it together.” Isaiah 40:3-5

Several hundred years after Isaiah prophesied, it is recorded that the prophet Malachi repeated to the people what the Lord said to him of a messenger being sent to clear the way before the Lord appeared. Malachi 3:1-5

How do we know this was the same one spoken of in the Old Testament?Matthew, referred to Isaiah’s words when he wrote about the baptism of Jesus.
“For this is the one referred to by Isaiah the prophet, saying, ‘The voice of one crying in the wilderness, make ready the way of the Lord, make His paths straight.’” Matt. 3:3

More information about John the Baptist is recorded in Luke. In the first couple of verses Luke says these stories were handed down by eyewitnesses but that he investigated them thoroughly. He tells more about the miraculous birth of this son to Zacharias and Elizabeth, both older adults without children. Zacharias, a priest in the temple, was considered righteous in the sight of God, blameless and keeping the commandments as well as his wife. One day while Zacharias was attending to his duties, the angel Gabriel, appeared to tell him that he would have a son and to name the child John, and that the child would be filled with the Holy Spirit while in his mother’s womb. Fear gripped Zacharias, but the angel told him not to be afraid that his son would be a forerunner to make ready a people for the coming of the Lord. But because he questioned the angel and the message, Gabriel told him he wouldn’t be able to speak until the child was born.

When Elizabeth was about 6 months with child, Gabriel appeared to Mary with a message from God. That she would be with child and she was to name him Jesus.
“He will be great and will be called the Son of the Most High; and the Lord God will give Him the throne of His father David, and He will reign over the house of Jacob forever, and His kingdom will have no end.” Luke 1:32-33

Gabriel also told Mary that her relative Elizabeth was also to bear a son. Mary hurried to the place where Zacharias and Elizabeth lived. Anxious to visit and to see that Elizabeth was with child even in her old age. It is recorded that when the baby in Elizabeth’s womb heard Mary’s voice, the baby leaped for joy and was filled with the Holy Spirit. What a blessing and encouragement it must have been to Mary as truths began to unfold to her. The first chapter of Luke very meticulously describes this event.

Fast forward to the baptism. Matthew records the conversation between John the Baptist, and Jesus at the Jordan River where Jesus had come to be baptized.
“Then Jesus arrived from Galilee at the Jordon to John, to be baptized by him. But John tried to prevent Him, saying, ‘I have need to be baptized by You, and do You come to me?’” Matt 3:13-14

What did HE say?

“Permit it at this time; for in this way it is fitting for us to fulfill all righteousness.” Matt 3:15

What did HIS Father say?

“And after being baptized, Jesus went up immediately from the water; and behold, the heavens were opened, and He saw the Spirit of God descending as a dove, and coming upon Him, and behold, a voice out of the heavens, saying, ‘This is My beloved Son, in whom I am well-pleased’.” Matt 3:16-17

This study can be used to prove that Jesus is who He claimed to be:

Prophesied 700 years prior to the incident.
John witnessed it as well as all those gathered at the baptism
They heard God speak
They testified to the facts
Apostles recorded it.
Especially Luke who states he investigated the handed-down story
and God said it!