Read John 8.
This chapter presents to us an extended argument between Jesus and the Pharisees (v. 13a). The argument began with a promise of Christ in verse 12, “I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life.”
Think about the implications of that promise. Without Christ, very little in this world makes sense. Why are we here? What happens after we die? Is this life all that there is? If so, why should I do anything other than what I want to do? Why should I do anything for others if it does not benefit me? Why should I respect their rights and avoid hurting others? But, if I just do what I want, then do I feel unfulfilled, even guilty? If this life is not all that there is, how can I know that?
Life is maddeningly strange without Christ and nothing really matters but your own pleasure, but living for pleasure is ultimately unsatisfying. Jesus came along and said, “Whoever follows me… will have the light of life.” Why? Because he is “the light of the world.” Knowing him, believing him, receiving his teaching and obeying it give you hope for the future and purpose for this life.
But how can you know if Jesus’s promise is true before you commit to it? There are several ways but the main one in this passage is the witness of the Father (vv. 14-30). Those who knew God (like Abraham) looked forward to the coming of Christ and prophesied about it (vv. 33-41, 54-59). Those who know God now recognize the authentic word of God in Jesus the Son (vv. 42-47). This is why the gospel brings conviction of sin and stirs the heart of those who hear it, even if they don’t receive it. It is the witness of the Father to the light-giving person of the Son.
If you’re reading this and, for some reason, have never received Jesus, this is God’s offer to you. Trust in Jesus, follow him, and he will give you the light that brings life (v. 12c). Only he can do this because only he is “the light of the world” (v. 12b).
For those of us who have received Jesus, this is why we must continually remind ourselves to trust God’s word in obedience instead of believing the lies of the devil and the world around us. They are not legitimate sources of light; following them means “walking in darkness.” Jesus rescued us from that, but we must continue to follow him to have his light illumine our path through this world.