The Greek word translated radiance is found only here in the New Testament. It means intense brightness. God's glory shows his presence (Exodus 16:7; 33:18; Isaiah 40:5). The Son's glory reflects God's glory, showing God's presence (Luke 9:32; John 1:14; 2:11; 17:5; Romans 8:17).
The Greek word translated exact representation is also unique in the New Testament. It refers to a mark like one on a coin. The Son clearly shows God's character (John 1:18; Philippians 2:6; Colossians 1:15).
His powerful word: This phrase means God's word is a strong and active force that created and controls the world (Hebrews 11:3; Psalm 33:6–11). The Son is also called "the Word of God" (Revelation 19:13; see also John 1:1–18).
He cleansed us from our sins (see Hebrews 9:11–10:18).
He sat down: This refers to Psalm 110:1 (see also Hebrews 1:13; 8:1; 10:12; 12:2). The Psalm predicted Christ's honor after his suffering (see Matthew 22:44; Acts 2:33; 1 Corinthians 15:25). The right hand of God shows high honor and position (see 1 Kings 2:19; Psalms 16:11; 45:4, 9; 80:17).