Let me drill down a little deeper into Jesus’ comment in verses 9-10. He said this as a parable about the Jews who threatened His life. Take a look at this translation (MKJV):
Jesus answered, Are there not twelve hours in the day? If anyone walks in the day, he does not stumble because he sees the light of the world. But if anyone walks in the night, he stumbles because there is no light in him.
What could those Jews do to Him? The “light of the world” is Jesus. As long as He was alive, His very Presence was a light brighter than the sun. Those Jews were forced to recognize the truth of things because Jesus demonstrated that truth in blinding glory. Once they had taken His life, they would be back in darkness and would no longer be able to hinder Him.
This whole chapter is about the very real Spirit Realm all around them. It might be invisible to eyes of the flesh, but it was obvious to anyone whose heart was awakened to see the moral truth of things. Those who put their faith in Jesus had the light of truth shining inside their souls. Once He was risen, it would be His own Spirit alive in them. The Jewish leaders would eventually kill Him, but that would only make His Presence greater, and would throw them back into darkness because they weren’t going to have that light shining inside of them. Their power ended with this life; God’s power had no limits.