In the NT, Hebrews is the only book that demonstrates a dedicated exposition of Scripture (the OT). Paul exegetes in letters; Acts records snippets; only Hebrews gives us a fulsome example.
Significantly, then, Hebrews should at the very least provide us with an elementary hermeneutical perspective and reservoir of exegetical techniques to both grasp the Scriptures and to use them for moral and spiritual edification.
Here is one such example that I find significant, though many could be given.
Hebrews 1 opens by asserting that God in many parts (i.e., partially or part-by-part) and in many ways (via prophets) communicated his revelation. In contrast, NOW he speaks in the Son (Heb 1.1-2).
Over the next two chapters, Hebrews cites the Scripture (the OT) and conveys divine conversations between Father and Son, where both speak directly.
That is, the Scripture (the OT) now in these last days conveys the word of Christ directly—now we can fully grasp the treasure hidden in the field of the OT (Scripture).
To preach Christ according to Scripture could only mean the OT since the NT had not been written. And that is the only Scripture we see preached in Acts and Hebrews.
Christ, according to Scripture, means that Scripture accords with the word of Christ because it IS the word of Christ.
God speaks when Scripture speaks. In these last days, we now hear the prophets for what they really said: through the divine Spirit, we hear God (the Son and Father) speak directly in Scripture.
The literal sense has become the Christological sense, not in a forced way, but in a revelation—a revealing of what Scripture has always said.