Psalm 2:7 is quoted in two different contexts in Hebrews, seeming to be used to support two vastly different arguments.
In Hebrews 1:5, we read
For to which of the angels did God ever say, “You are my Son, today I have begotten you”? Or again, “I will be to him a father, and he shall be to me a son”? (Hebrews 1:5 ESV)
where Psalm 2:7 is apparently used to support Auctor's sustained argument that Jesus is better than angels.
A couple of chapters later, however, the verse is quoted again
So also Christ did not exalt himself to be made a high priest, but was appointed by him who said to him, “You are my Son, today I have begotten you”; (Hebrews 5:5 ESV)
This time, the Psalm is apparently used to prove that Jesus did not take the priesthood upon himself (see, e.g., v4).
And yet, when reading Psalm 2, this stanza seems to refer to a decree in which God appointed the King (whether David, or Jesus, or both).
What is going on? These two verses seem to pay no attention to the original context, and simply use these words to augment an argument that is made before even approaching the text. To put it more provocatively, the usage here seems to be eisegesis or, perhaps, prooftexting.
What is Auctor's approach to Psalm 2:7 when he uses it in 1:5 and 5:5?