The English word witness translates a Greek word μαρτυρία in John 1.7: He [John] came as a witness, to bear witness about the light. Witness is a pretty good translation of the word because in the Greek it means: “confirmation or attestation on the basis of personal knowledge or belief, testimony” (BDAG). We have witnesses in our courts of law because they have personal knowledge of whatever it is that is being adjudicated in the court. We don’t ask for volunteers as if to say, “Hey, does anyone want to comes as a witness on whether or not Johnny stole 6 bottles of 5 hour energy from the 7-11 and drank them?” Nope. You must have seen Johnny steal and drink the bottles in order to be a witness. The word that John uses is the same here. John the Baptizer came as a witness to Christ because he had personal knowledge of Christ.
Witness is one of the major words in the book of John. He uses the noun or verb form of witness 57 times. Contrast his use with the other three gospels. In total they only use the noun or verb form of witness 5 times! Think John is trying to tell us something here? (Hint: See John 20.31 for answer).
John weaves witnesses throughout his gospel and they are all witnessing to Jesus. Bob Utley in his study guide on John points out that: John the Baptist witnesses to Christ (here, 3.26,28; 5.33); Jesus witnesses to himself (3.11;5.31); the Samaritan woman witnesses to Christ (4.29); God the Father witnesses to Christ (John 5.32,34,37); Scripture witnesses about Christ (5.39); the crowd at Lazarus’ raising from the dead witness to Christ (12.17); the Spirit witnesses (15.26-27); the disciples witness (15.27); the author witnesses (21.24). All of these are witnesses to Christ. John piles up the evidential witnesses over and over so we do not—indeed we cannot—miss what he wants us to see: That you (dear reader) might believe that Jesus is the Christ, the son of God, and that by believing you may have life in his name.
The question that arises is pretty obvious: Do you believe John’s lineup of witnesses?