“He is the radiance of the glory of God and the exact imprint of his nature, and he upholds the universe by the word of his power” (Hebrews 1:3).
Behind our two words “exact imprint” there is one Greek word: character. The word literally means “an imprint or carving,” and is used, for instance, to refer to the stamp of a ruler on coins. Thus, Jesus is the exact imprint of the nature and being of God. When one looks at Jesus, one sees a perfect representation of who God really is, how God really thinks, and how God really acts. Jesus is a portrait in being of the Father’s being. Whereas coins offer an impersonal representation of a ruler, Jesus offers an ultimately personal representation of the Father. “Whoever has seen me has seen the Father” (John 14:9).
Why are these two facts juxtaposed in this verse, namely, that Jesus “is the radiance of the glory of God AND the exact imprint of his nature”? Simply this: many things shine brightly but do not represent God rightly.
The devil appears as an angel of light, but his light is all darkness (2 Corinthians 11:14). The world shines bright in all is glitz and glamour, but in the end its light is all darkness. There are many ways that seem right and light and bright to a man, but in the end they lead to death and they are all darkness (Proverbs 14:12).
But Jesus shines brightly precisely because he represents the Father rightly, and he represents the Father rightly because he shares in his very being and nature. He is the "exact imprint" of the nature of God, he is a portrait in being of the Father’s being, and therefore he is the radiance of the glory of God.