Hebrews 1
The Deity of Christ — Hebrews 1:1-4
Heb 1:1-4 opens with the Son as "the radiance of the glory of God and the exact imprint of his nature," who "upholds the universe by the word of his power." The Son is not a creature but the eternal heir of all things. Athanasius marshalled this text against any subordination of the Son, and Nicaea confessed him 'true God from true God'. The catena of Old Testament quotations that follows in Hebrews 1 applies divine titles directly to Christ. The creative agency of 1:2-3 matches the Logos of John 1:3 and the cosmic Christ of Col 1:16-17. Aquinas treats the Son's consubstantial glory as the basis of his priestly mediation, which Hebrews will develop in chapter 9.
The Eternal Generation of the Son — John 5:26
John 5:26 is a key text for eternal generation: "as the Father has life in himself, so he has granted the Son also to have life in himself." The Son's life is the Father's own life, eternally communicated. Nicaea confessed the Son 'begotten, not made,' eternally from the Father, and Augustine guarded this against any temporal subordination. Aquinas treated generation as an eternal act of the divine intellect. The mutual life of Father and Son connects to the Logos who was with God in John 1:1 and to the radiance of God's glory in Heb 1:3. Generation is eternal, not an event within time.