1:8 unto the Son. Christ is the Son of God by: resurrection (Hebrews 1:5a; Acts 13:33; Romans 1:4); human generation (Hebrews 1:5b; Luke 1:33); proclamation (Hebrews 1:6; Matthew 3:17); nature (Hebrews 1:8-9; John 10:30); eternal generation (Hebrews 1:10-12; Colossians 1:15); and inheritance (Hebrews 1:13; Hebrews 1:2). In contrast to the eternal Son, angels are sons of God by special creation (Job 38:7; Psalm 104:4-5).

1:8 he saith. See Psalm 45:6-7.

1:9 God, even thy God. The testimony of Psalm 45:6-7 as quoted here is clearly Messianic; it is both addressed to God (note “thy throne, O God”—Hebrews 1:8) and spoken about God (“God, hath anointed thee…”). One person of the Godhead is speaking to another Person of the Godhead.