We see one of the greatest manifestations of the Trinity in the Bible, on that beautiful day when Jesus appeared at the River Jordan, where John the Baptist was Baptizing those gathered.
It begins when John sees Jesus approaching, and announces Jesus for who He Truly is:
John 1:29 -34 – “The next day John sees Jesus coming unto him, and said, Behold the Lamb of God, which takes away the sin of the world. This is He of Whom I said, After me comes a Man which is preferred before me: for He was before me. And I knew Him not: but that He should be made manifest to Israel, therefore am I come baptizing with water. And John bear record saying, I saw the Spirit descending from heaven like a dove and it abode upon Him. And I knew Him not: but He Who sent me to baptize with water, the same said unto me, Upon Whom you shall see the Spirit descending, and remaining on Him, the same is He which baptizes with the Holy Spirit. And I saw, and bear record that this is the Son of God.”
Now when Jesus tells John to Baptize Him, John argues that it is not he who should baptize Jesus, but Jesus to Baptize him.
Matthew 3:13-15 – “Then came Jesus from Galilee to Jordan unto John, to be baptized of him. But John forbad Him, saying, I have need to be baptized of You, and come You to me? And Jesus answering said unto him, Suffer it to be so now: for thus it becomes us to fulfill all Righteousness. Then he suffered Him.”
Upon hearing this Truth spoken by Jesus, John baptized Him in water. It is then that we witness that beautiful and Glorious moment when the entirety of The Godhead is revealed to all present.
Mark 1:9-11 – “And it came to pass in those days, that Jesus came from Nazareth of Galilee, and was baptized of John in Jordan. And straightway coming up out of the water, he saw the Heavens opened, and the Spirit like a dove descending upon Him: And there came a Voice from Heaven saying, You are My Beloved Son, in Whom I am well pleased.”