Prophets represent God, yet the Old Testament also emphasizes that God himself is uniquely the source of light and salvation.
Isaiah 40:9-11; Isaiah 60:1-3 provide useful background.
At the close of his public ministry Jesus identifies response to himself with response to the Father and claims that seeing him is seeing the Father who sent him.
The statement anticipates John 14:9 and strengthens the Gospel's theme that the invisible God is uniquely made visible in Jesus.