I was reminded in Hebrews class again today of the complete inadequacy of the older evangelical hermeneutical paradigm. It was not wrong on the original meaning (although it frequently cheated with its own method). It was wrong rather about its canons of application (e.g., the vastly inadequate Fee and Stuart motto--it can't mean something it never meant).
The use of Psalm 40 in Hebrews 10 is an excellent case in point because it foils all the coping mechanisms of the older paradigm.
For example, it is clear that the original meaning of Psalm 40 was not about Jesus. Psalm 40:13 mentions the iniquities of the psalmist. In the original meaning of the psalm, therefore, Psalm 40:6-8 were not Jesus speaking but the psalmist speaking.
Secondly, the original meaning surely was not meant to do away with sacrifices entirely any more than the critiques of Psalm 51, Isaiah 1, Micah 6, or Jeremiah 7 were (unless you want to say that these verses contradict Leviticus at the very core). When Hebrews reads these words on the lips of Jesus as an indication that his death does away with the sacrificial system, this is a quite significantly different meaning than the passage had originally.
The author of Hebrews, as it were, lifts a section of this psalm from its context on the lips of David (as he would have likely read it) and figuratively places it on the lips of Jesus as he enters the world. I say figuratively because are we really to suppose that the author pictures Jesus literally saying these words as he descends through the clouds? It seems more likely that the author is simply expressing the purpose of Jesus taking on a body.
Perhaps the most interesting point is that the author of Hebrews is making his point from the Greek translation of the OT which reads differently from the original Hebrew. The Hebrew says, "my ears you have opened." The Greek reads, "a body you have prepared." We therefore face a choice. Are we going to accept that inspiration is not limited to the original meaning--indeed to the original text--or is inspiration of the biblical authors a spiritual task that was not limited by the historical or the original meaning?
By the way, this phenomenon also legitimates textual criticism and deconstructs a King James only perspective. Both texts can't be original. If a KJV person considers the reading of Hebrews 10 original, then its version of Psalm 40 is not original. But if a KJV person considers the reading of Psalm 40 original than its version of Hebrews 10 is not original.