In verse 6, a new participant is introduced, a man sent from God whose name was John. This John is not the author of the book, the apostle, but rather John the Baptist. But the first glimpse into his ministry in this Gospel is not a narrative of what he was doing (as will come after John’s Prologue and we see in Matthew chapter 3 and Mark chapter 1), nor is it to do with his forecasted birth (as in Luke’s Gospel), but simply with his purpose in coming.
Why was John sent from God? He came as a witness to bear witness to the light, so that all might believe through him. Notice the purpose clauses: he came as a witness in order to bear witness to the light and the reason given for this bearing witness is in order that all might believe through him.
But, lest someone mistake John for the light or give him more credit than is due, verse 8 reminds us that he was not the light, but came to bear witness about the light. John the author again uses a repetition in the negative as he did for creation and the Word in verse 3.
John’s entire ministry can be summed up here: to bear witness to the light and thereby see people believe in the light. And in this text, the light is not simply an abstract notion (though it ties into the abstract notion used throughout the Gospel) but is the Word introduced in the first few verses that we were told is the light of all people: the second person of the trinity, God’s divine self-expression, the revelation of God, Jesus himself. John was sent by God to testify about Jesus so that people would believe in him.
How he does this will be the subject of 1:15 and 1:19ff. in a few studies time.