God's glory

In 2 Corinthians 4 Paul probably was probably remembering his experience on the road to Damascus. Then he saw the light from heaven. The light came from God who created light (Genesis 1:3). This links original creation with the new spiritual creation in Christ (2 Corinthians 5:17). Paul had seen the face of the Son of God in the blinding light, which overwhelmed him on his way to Damascus (to persecute the Christians there) and he identified the face of Christ with the glory of God.