Matthew 21:25
"The baptism of John, whence was it? from heaven, or of men? And they reasoned with themselves, saying, If we shall say, From heaven; he will say unto us, Why did ye not then believe him?"
Cross References (ranked by relevance)
John 1:15
John bare witness of him, and cried, saying, This was he of whom I spake, He that cometh after me is preferred before me: for he was before me.
John 3:18
He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
Luke 20:5
And they reasoned with themselves, saying, If we shall say, From heaven; he will say, Why then believed ye him not?
John 1:6
There was a man sent from God, whose name was John.