Jesus was announced by John
There came a man sent from God, whose name was John. He came as a witness about the Light, so that all might believe through him. He was not the Light, but he came to testify about the Light.
John continues his progression and now picks up the redemptive recap with John the Baptist, who was a witness about the Light. He also continues with the use of the figurative word Light. The NASB capitalizes the word indicating its true reference to Jesus (just as it did with the word “Word”). The use of Light in this text draws us deeper to what John is communicating here about the coming Christ.
John Calvin, in his commentary, broke the word down to the meaning of enlightenment (or relating to the mind) of man. In other words, the emphasis of the word Light when used here to refer to Jesus, is to emphasize that God communicated to man by appealing to their mind when God was incarnated. In other words, Jesus is the most accurate representation of the mind of God that man can comprehend. God is appealing to the “light of man” with the “Light of God.” To put more plainly, God is appearling to the mind of man with the mind of God.
The mind of God is best expressed in Jesus Christ. He is the most accurate visible representation of God that man has ever gazed upon. For this reason, the NASB has capitolized the word Light – implying that it is pronoun for the Christ. A light is the radience of energy. Christ is the radience of God.
Following this train of thought, it is reasonable to refer to Christians as the “light of the world” although a capitol is not needed. So in verses 6-8, John describes the Baptist as one who was not the Light but the one who testifies about the Light. Thus, John was a light himself, but a much more dimmer one. He was not Jesus, but he did prepare and point others to Jesus.
The word testify is a courtroom term that means “to bear witness.” John the Baptist was one who went before Jesus and created expectancy for Him. His role was to prepare the hearts of man in order that they may have faith in Christ when He comes. John was the agent of belief, while Jesus was the object of belief.
This was just another way that God made Himself known to men. Yet He was still rejected because “the darkness did not comprehend it” (John 1:5).