I suppose John initially may have imagined that Jesus was coming towards him to destroy him. We can see that he crumpled, so astounded and afraid was he. He must have been afraid because Jesus told him not to fear. There is an obvious sense in which this incident is like how Isaiah reacted when he had a vision of the greatness of Jesus in Isaiah 6.
From some points of view, the response of John is surprising. When Jesus was here on earth with his disciples, John had a very close relationship with Jesus, expressed in how he used to lean Jesus’ breast. Moreover, it is possible that Jesus and John were cousins because a case can be made for saying that John’s mother Salome and Mary were sisters. Why did John now respond in this way? He had new insights into his own nothingness and into the greatness of Jesus.
John’s response tells us how wrong it is to be flippant about Jesus. He is not only great in prestige, he is full of power, and when in his presence one is very much aware of who he is. John’s response was that he knew he should bow, but not bow as a merely symbolic gesture. The apostle does not only have a mental grasp of the greatness of Jesus, he feels it and is compelled to fall at his feet.
It is important to confess the greatness of Jesus. And doing so for John led to words of assurance from Jesus, which we can think about tomorrow.