The light shines in the darkness, and the darkness has not overcome it.
John 1:5 ESV
The Grace of our Christian Hope is in Christ Jesus (John 1:14). But what is the hope of our grace? In other words, how do we know for sure that this grace that we have in Christ Jesus is truly effective? That is where John 1:5 helps us.
This is the hope of our grace: That Jesus, the source of our Grace, is the light that shines in the darkness. And this darkness cannot overcome it. If Jesus' victory over darkness is transient and could be possibly overturned, the promise is similarly fragile. But the promise of grace is of eternal assurance because Jesus is the light that darkness cannot overcome.