John 1:8

He was not the Light, but he existed that he might give testimony concerning the Light.

John 1:20

He avowed--he did not conceal the truth, but avowed, "I am not the Christ."

John 3:28

You yourselves can bear witness to my having said, 'I am not the Christ,' but 'I am His appointed forerunner.'

Acts 19:4

"John," he said, "administered a baptism of repentance, bidding the people believe on One who was to come after him; namely, on Jesus."

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
He avowed--he did not conceal the truth, but avowed, "I am not the Christ."
John 3:28
You yourselves can bear witness to my having said, 'I am not the Christ,' but 'I am His appointed forerunner.'
Acts 19:4
"John," he said, "administered a baptism of repentance, bidding the people believe on One who was to come after him; namely, on Jesus."

General references

Mark 11:30
John's Baptism--was it of Heavenly or of human origin? Answer me."
Acts 13:24
Before the coming of Jesus, John had proclaimed to all the people of Israel a baptism of repentance.