John 1:7 (ESV) … “He came as a witness, to bear witness about the light, that all might believe through him.”
John the Baptist’s function was to be a channel whereby people could come to Christ. Jesus called John the Baptist the greatest man ever born (Luke 7:28) because he fulfilled the highest privilege; he was the first to point people to Christ, so in a very real sense, all who have come to believe have done so because of his witness. He was first in a line of witnesses that stretches through the centuries to this day.
John stressed the difference between John the Baptist and Jesus, even though to many it might have been obvious, because even during Paul’s travels, he encountered believers who only knew about John the Baptist but not about Jesus (see Acts 18:25; 19:1–7). John the Baptist influenced the people of Ephesus where John had written this Gospel. John wanted to ensure that all believers worship Christ, not his messenger.
Like John the Baptist, we are not the source of God’s light; we merely reflect that light. Jesus Christ is the true Light; he helps us see our way to God and shows us how to walk along that way. But Christ has chosen to reflect his light through his followers to an unbelieving world, perhaps because unbelievers are not able to bear the full blazing glory of his light firsthand. The word witness indicates our role as reflectors of Christ’s light. We are never to present ourselves as the light to others, but are always to point them to Christ, the Light.