The above topic is a crucial question any believer may encounter, and there is a need to get a clear answer according to God's word. Bro Eli shared this teaching in a simpler way one can understand.
First, he made us know the need to understand that baptism was part of the fulfilment of what was written in the scriptures for Christ. See in Matthew 3:13-15
KJV:Then cometh Jesus from Galilee to Jordan unto John, to be baptized of him.
KJV:But John forbad him, saying, I have need to be baptized of thee, and comest thou to me?
KJV: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.
From the above scripture - Baptise me now, John, to fulfil all righteousness. What was the righteousness to fulfil? Hebrews 10:7 made us understand that there are things that were exclusively written for Christ to fulfil. And He fulfilled them all, including the baptism.
KJV:Then said I, Lo, I come (in the volume of the book it is written of me,) to do thy will, O God. Hebrews 10:7
Hebrews 10:7 was the statement Jesus made for us to understand that He did not come on His own, but came according to what was written about Him.
In Luke 24:44, Jesus shared -
KJV:And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me.
Meaning, there are things that were written in the law of Moses, Psalms and other old testament for Christ to fulfil. Therefore, there was a need for John to baptise Christ - to fulfil what was written of Him.
The book of Isaiah 40:3 was the prophecy exclusive for John and Christ.
KJV:The voice of him that crieth in the wilderness, Prepare ye the way of the Lord, make straight in the desert a highway for our God.
It was John to prepare the way for Christ, his baptism was for repentance and remission of sin but while baptising, Jesus came and asked him to baptise Him.
John knowing that Jesus was to come and take away the sins of the world, he felt reluctant to do it. Thereafter, having understood Christ's essence of fulfilling the scriptures, he submitted to baptise Him.
Matthew 3:15 shows Jesus' statement to him -
KJV: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.
Finally, according to Bro Eli, the essence of Christ's baptism was to give an example to His followers.