“The Son is the radiance of God’s glory and the exact representation of his being, sustaining all things by his powerful word. After he had provided purification for sins, he sat down at the right hand of the Majesty in heaven.” Hebrews 1:3
“The radiance of God’s glory” means God has revealed the light of His glory in Christ Jesus through “the exact representation of His being”. As a wax mold reveals every detail of an object, Jesus is the exact expression of the Father’s nature, being eternally begotten of the Father. He possesses and reveals all that is divine. To see Jesus is to see the Father. The author of Hebrews is also emphasizing that this is not a reflected brightness like the light of the moon. Instead this is an inherent brightness like a ray from the sun. Jesus’ glorious brightness comes from being essentially divine.
“By His powerful Word” means that Jesus, the Word who called creation into being as recorded in Genesis 1, continues to uphold all creation.
“Purification for sins” is a reference to the blood of sacrificed animals, which cleansed both the Old Testament temple’s altar and God’s people from the defilement caused by sin. Jesus alone makes the final, complete purification of our sinful condition. The glory of redemption is far greater than the glory of creation. The Son of God came down not to dazzle us with His splendor but to purge our sins.
”Sat down” suggests the formal act of assuming the office of High Priest and implies a contrast to the Levitical priest, who never finished his work and sat down. In the Old Testament we meet a seatless sanctuary; while in the New Testament we find a seated Savior.
Blessings on your day…