The epistle “to the Hebrews” is a “brief word of exhortation” (Hebrews 13:22).
What is being exhorted? That we should listen to the voice of the Son of God (see specifically Hebrews 1:1-2; 2:3; 3:7-11, 14-15; 4:7; 5:11; 8:10; 12:25 for the recurrence of this theme). For this reason, the letter can be regarded as an exposition of, or an elaboration on, this New Testament verse:
Matthew 17:5 While he was still speaking, a bright cloud overshadowed them, and behold, a voice out of the cloud said, “This is My beloved Son, with whom I am well-pleased; listen to Him!”
For the same reason, the letter to the Hebrews can be regarded as reinforcing this Old Testament verse as well:
Deuteronomy 18:15 “The LORD your God will raise up for you a prophet like me from among you, from your countrymen, you shall listen to him.
Through the resurrection of Jesus Christ from the dead, all Scripture is revealed as pointers to Him…that we might listen to Him.
Scripture quotations taken from the NASB, unless otherwise noted.