John 1:8

That man was not the light, but that he might testify about the light.

John 1:20

And he confessed, and did not deny, and confessed, I am not the Christ.

John 3:28

Ye yourselves testify that I said, I am not the Christ, but that I am sent ahead of that man.

Acts 19:4

And Paul said, John indeed immersed an immersion of repentance, saying to the people that they should believe in him who was coming after him, that is, in Jesus, the Christ.

Treasury of Scripture Knowledge

Summary

He was not that Light, but was sent to bear witness of that Light.

General references

Bible References

That light

John 1:20
And he confessed, and did not deny, and confessed, I am not the Christ.
John 3:28
Ye yourselves testify that I said, I am not the Christ, but that I am sent ahead of that man.
Acts 19:4
And Paul said, John indeed immersed an immersion of repentance, saying to the people that they should believe in him who was coming after him, that is, in Jesus, the Christ.

General references

Mark 11:30
The immersion of John, was it from heaven, or from men? Answer me.
Acts 13:24
John having earlier proclaimed, before his coming presence, the immersion of repentance to Israel.