A.T. Robertson Commentary John 8:12

"Again therefore Jesus spake unto them, saying, I am the light of the world: he that followeth me shall not walk in the darkness, but shall have the light of life." — John 8:12 (ASV)

Again therefore (παλιν ουν). This language fits in better with 7:52 than with 8:11. Just suppose Jesus is in the temple on the following day.

Unto them (αυτοις). The Pharisees and crowds in the temple after the feast was past.

I am the light of the world (εγω ειμ το φως του κοσμου). Jesus had called his followers "the light of the world" (Matthew 5:14), but that was light reflected from him. Already Jesus (the Logos) had been called the true light of men (1:9; 3:19). The Psalmist calls God his Light (27:1). So Isa 60:19. At the feast of tabernacles in the Court of the Women where Jesus was on this day (8:20) there were brilliant candelabra and there was the memory of the pillar of cloud by day and of fire by night. But with all this background this supreme and exclusive claim of Jesus to being the light of the whole world (of Gentiles as well as of Jews) startled the Pharisees and challenged their opposition.

Shall have the light of life (εξε το φως της ζωης). The light which springs from and issues in life (Westcott). Cf. 6:33,51 about Jesus being the Bread of Life. In this sublime claim we come to a decisive place. It will not do to praise Jesus and deny his deity. Only as the Son of God can we justify and accept this language which otherwise is mere conceit and froth.