Our Witness Is A Great Necessity
"John was a man, that is, a human. This is important because up till now the Word, Jesus Christ, has been called God the Creator of all things. In him was life, and that light was the light of men. So it looks as if the way this Word and Life and Light are going to spread through the world is by its own sovereign power and brightness. But John knows that is not the case. This Word and Life and Light are going to spread through the witness of human beings—and no other way." Piper goes on to explain that saying a human witness was needed does not mean that it was necessary for God to use a human, but rather shows when God wants to use a witness, he sends a witness. We are reminded of John 20:21 "As the Father has sent me, I am sending you."
Piper continues that we serve a God who saves and sends. He says
" We serve a saving and sending God. He provides the foundation of our salvation in Jesus Christ, and he provides the means of our salvation in those whom he sends. Let this have an enlivening effect on you. God is at work now—today—moving his witnesses through the world, making them the means of his saving work. I hope this makes you want to look Jesus square in the face and say with Isaiah, 'Here am I! Send me'"In Verse 7 John mentions “. . . that all might believe through him.” This is the first mention of believing in John's Gospel. It occurs 97 more times.
Piper ends the point on the necessity of the human witness.
"Our witness is a great necessity. Without a witness no one believes. Verse 7: “He came as a witness, to bear witness about the light, that all might believe through him.” Through him. Through his witness. That’s how necessary it is. Believing only happens through a witness."