John 1:7

The same came for a testimony, that he might testify concerning the Light, that all might believe through him.

John 1:19

And this is the testimony of John, when the Jews sent forth priests and Levites from Jerusalem, to ask him, "Who are you?"

Acts 19:4

And Paul said, "John immersed with an immersion of repentance, saying to the people that they should believe on Him coming after him; that is, on Jesus."

John 1:9

He was the true Light That lighteth every man coming into the world.

John 1:12

But as many as received Him, to them He gave the right to become children of God, to those believing in His name;

John 1:15

John testifies concerning Him, and has cried, saying, "This was He of Whom I said, 'He That cometh after me hath become before me, because He was before me;'"

John 1:26-27

John answered them, saying, "I immerse in water: in your midst standeth One Whom ye know not??27 the One coming after me, the latchet of Whose sandal I am not worthy to unloose."

John 1:32-34

And John testified, saying, "I have beheld the Spirit descending as a dove out of Heaven, and He abode upon Him.

John 1:36

and, looking upon Jesus as He was walking, says, "Behold, the Lamb of God!"

John 3:26-36

And they came to John, and said to him, "Rabbi, He Who was with you beyond the Jordan, to Whom you have borne testimony, behold, He is immersing, and all are coming to Him."

John 5:33-35

Ye have sent to John, and he has testified to the truth.

Ephesians 3:9

and to plainly show what is the dispensation of the mystery which from the ages has been hidden away in God, Who made all things;

1 Timothy 2:4

Who wisheth all men to be saved, and to come into a full knowledge of truth.

Titus 2:11

For the salvation-imparting grace of God appeared to all men,

2 Peter 3:9

The Lord is not slow respecting the promise, as some account slowness; but He is long-suffering toward you, not wishing that any should perish, but that all should come to repentance.

Treasury of Scripture Knowledge

Summary

The same came for a witness, to bear witness of the Light, that all men through him might believe.

General references

Bible References

A witness

John 1:19
And this is the testimony of John, when the Jews sent forth priests and Levites from Jerusalem, to ask him, "Who are you?"
John 3:26
And they came to John, and said to him, "Rabbi, He Who was with you beyond the Jordan, to Whom you have borne testimony, behold, He is immersing, and all are coming to Him."
John 5:33
Ye have sent to John, and he has testified to the truth.
Acts 19:4
And Paul said, "John immersed with an immersion of repentance, saying to the people that they should believe on Him coming after him; that is, on Jesus."

That

John 1:9
He was the true Light That lighteth every man coming into the world.
John 3:26
And they came to John, and said to him, "Rabbi, He Who was with you beyond the Jordan, to Whom you have borne testimony, behold, He is immersing, and all are coming to Him."
Ephesians 3:9
and to plainly show what is the dispensation of the mystery which from the ages has been hidden away in God, Who made all things;
1 Timothy 2:4
Who wisheth all men to be saved, and to come into a full knowledge of truth.
Titus 2:11
For the salvation-imparting grace of God appeared to all men,
2 Peter 3:9
The Lord is not slow respecting the promise, as some account slowness; but He is long-suffering toward you, not wishing that any should perish, but that all should come to repentance.

General references

Mark 11:30
The immersion of John, was it from Heaven, or from men? Answer Me."
Acts 13:24
John having first preached, before His coming, the immersion of repentance to all the people of Israel.