R.C Sproul had this to say about D.A. Carson,
"The leading and finest NT scholar on this planet is... Dr. D.A. Carson." (You can hear the quote here.)
These are no small words. It is an incredible endorsement. While my own opinion is like a fleck of sand in comparison to that of R.C. Sproul, I cannot help but agree. Carson keeps his finger on the text of Scripture like few others.
In a recent series of lectures (the 2013 TEDS Lecture Series), Carson works his way through the book of Hebrews, hitting the high points of the epistle. Now of particular interest, and it is that which I'd like to draw your attention, is the fourth lecture. Dr. Carson's handling of the seventh chapter of Hebrews will no doubt hit a reformed nerve. His exegetical conclusions aren't classically Reformed. So let that be clear. Discernment should be exercised (as always).
However, Carson here can and ought to serve as an excellent exegetical sparring partner. Not only in general, but in particular. Here I am thinking of those who hold certain convictions about Christmas and the regulative principle of worship.
One grouping of questions that deserves to be considered is the role of Hebrews 7:12 with respect to the regulative principle of worship. What is the extent of the change of law? How might it nuance our view (if at all) of the RPW? Ignoring questions of continuity and discontinuity (for the sake of sharpening an exercise), what might one deduce about the RPW from the New Covenant as a distinct body of instruction? What does it teach?
For myself, these are tricky questions. I suspect that wherever one lands on the particulars of Christmas, wrestling with these issues will help sharpen their view.
You can find the lectures here. Again, all of them are good, but the fourth is where a good portion of the action is found.