Post tenebras Lux- translated, “After darkness, light,” is a Latin phrase the reformers (Martin Luther, namely- John Calvin) adopted after the reverence and glory of the Gospel was once again restored to the people, through the Reformation.
This phrase also reminds of 2 Corinthians 4:5-6 “For what we proclaim is not ourselves, but Jesus Christ as Lord, with ourselves as your servants for Jesus’ sake. For God, who said, let light shine out of darkness, has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ.”
In the darkness, the star of Bethlehem shone down on the people proclaiming the the light of the world has come. Now, we are commissioned to be lights of the world sharing the Gospel for the glory of God. Matthew 5:14-16