John 12:46
“I have come a light into the world.”
For since the Father is called by this name everywhere both in the Old (Testament) and in the New, Christ uses the same name also; therefore Paul also calls Him, “Brightness”, having learned to do so from this source. And He shows here His close relationship with the Father, and that there is no separation between them, if so be that He says that faith on Him is not on Him, but passes on to the Father. And He called Himself “light,” because He delivers from error, and dissolves mental darkness.
Source: Homilies on the Gospel of John (New Advent)