John the Baptist – was out in the wilderness, baptizing Jewish people in the Jordan River.
One day, Jesus walked to where John was.  When John saw Jesus, he said an astounding thing; ‘Behold the Lamb of God who takes away the sin of the world!’  John 1:29

What John knew about Jesus:
John knew – Jesus, the Man was higher in rank than himself. 
John knew – Jesus existed before he (John) was born.
In fact, Jesus existed at the creation of the world. 
NASB John 1:1-2 “In the beginning was the Word (Jesus), and the Word was with God, and the Word was God.
2 He (Jesus) was in the beginning with God.”

What John testified from personal knowledge:
NASB John 1:32-33 “John testified saying, ‘I have seen the Spirit descending as a dove out of heaven, and He (Holy Spirit) remained upon Him (Jesus).”
33 ‘I did not recognize Him (Jesus), but He (God the Father), who sent me to baptize with water said to me, ‘He upon whom you see the Spirit descending and remaining upon Him, this is the One who baptizes with the Holy Spirit.”

John’s astonishing  testimony – given without a doubt:
NASB John 1:34 “I myself have seen, and have testified that this is the Son of God.’”

~ Take it to heart ~

Think about this:
What do you know without a doubt about Jesus?