13 Then the Pharisees said to him, "You are testifying on your own behalf; your testimony is not valid." 14 Jesus answered, "Even if I testify on my own behalf, my testimony is valid because I know where I have come from and where I am going, but you do not know where I come from or where I am going.
Matthew Henry's Commentary on John 8:13-14
Commentary on John 8:12-16
(Read John 8:12-16)
Christ is the Light of the world. God is light, and Christ is the image of the invisible God. One sun enlightens the whole world; so does one Christ, and there needs no more. What a dark dungeon would the world be without the sun! So would it be without Jesus, by whom light came into the world. Those who follow Christ shall not walk in darkness. They shall not be left without the truths which are necessary to keep them from destroying error, and the directions in the way of duty, necessary to keep them from condemning sin.