John 1:15

John bore witness of Him and cried out, “This was He of whom I said, ‘He who comes after me is preferred before me, for He was before me.’ ”
John 1:15, Modern English Version (MEV)
 
Just to reiterate, in case we missed it the first million times, the Word Who became flesh, this Jesus, is the same One Whom John the Baptizer spoke about during his ministry.
 
As Albert Barnes tells us in his Notes on the Bible:

John bare witness of him - The evangelist now returns to the testimony of John the Baptist. He had stated that the Word became incarnate, and he now appeals to the testimony of John to show that, thus incarnate, he was the Messiah.

He that cometh after me - He of whom I am the forerunner, or whose way I am come to prepare. See the notes at Mat_3:3.

Is preferred before me - Is superior to me. Most critics have supposed that the words translated “is preferred” relate to “time,” and not to “dignity;” meaning that though he came after him publicly, being six months younger than John, as well as entering on his work after John, yet that he had existed long before him. Most, however, have understood it more correctly, as our translators seem to have done, as meaning, He was worthy of more honor than I am.

He was before me - This can refer to nothing but his pre-existence, and can be explained only on the supposition that he existed before John, or, as the evangelist had before shown, from the beginning. He came “after” John in his public ministry and in his human nature, but in his divine nature he had existed long before John had a being - from eternity. We may learn here that it is one mark of the true spirit of a minister of Christ to desire and feel that Christ is always to be preferred to ourselves. We should keep ourselves out of view. The great object is to hold up the Saviour; and however much ministers may be honored or blessed, yet they should lay all at the feet of Jesus, and direct all men to him as the undivided object of affection and honor. It is the business of every Christian, as well as of every Christian minister, to be a witness for Christ, and to endeavor to convince the world that he is worthy of confidence and love.