To Which of the Angels Did God Ever Say…
The writer of Hebrews starts his exhortation to the Hebrew Christians by proving the deity of the Son of God & his supremacy over angels from the Old Testament.
Studying the angel of Jehovah (the Lord) led to another reference to the same angel: the angel of Elohim (God). Sometimes the angel references God in the 3rd person, as we would expect (God being another person), but sometimes the angel speaks of Jehovah in the 1st person, as if he is Jehovah.
Gen 16:11, The angel of Jehovah says Jehovah heard the boy’s (Ismael’s) cries
Judges 6:11-22, The Bible identifies the angel as Jehovah
The angel speaks in 1st & 3rd person as Jehovah
Zech 3:1-2, Of the angel it says, "…Jehovah said to Satan, ‘Jehovah rebuke you, O Satan!'"
But the angel is not God the Father,
Zech 1:7-17, The angel & Jehovah of hosts converse with each other.
The angel himself is God.
Judges 2:1-5, "I brought you out of Egypt…"
The angel speaks for God the Father
Zech 3:5-7, "Thus say Jehovah of hosts…"
The angel identified as Jesus
Zech 12:1-10, The house of David shall be like the angel of Jehovah… when they look on me, on [the one] they have pierced…
So what does this have to do with Hebrews? It answers the writer’s question: "to which of the angels did God ever say… You are my Son…," it is not: none. The answer is: The angel of Jehovah/Elohim. The angel who IS the Son of God. The writer himself is affirming Jesus is that angel, the angel who is God.