The author of this letter to the Hebrews' is unknown, but it was possible written by the apostle Paul and was written before AD70 to inspire confident in the Hebrew believers, who where suffering from persecution and considering going back to Judaism. The books key words are "Better x 13" and "Perfect x 7" In Chapters 1 to 10;18  he gives teaching, pointing them to the Preeminence of Christ and His message and His Glory. Jesus Christ is far far Better than all the rights and rituals and sacrifices of the Old Testament. For Christ Jesus is far Better yes He is superior greater than all the prophets, the angels, the high priest, and Better than Moses etc. plus he gives four exhortations to "Let Us" Fear, Labour, Come Boldly to a throne of grace, Go on. Then In Chapter 10;19 to 13;25 he gives seven more Exhortations to "Let us" Draw Near, Hold Fast, Consider one another, Lay aside every weight, and run with patience, Have Grace, Go Forth, Offer the Sacrifice of Praise. So, keep to your faith in Jesus Christ, Warning them of the perils of backsliding. Also of the blessings and duties of their faith in Christ. As Hebrews 13;8. says "Jesus Christ is the same yesterday today and for ever" so keep the Faith, and only rest your Hope and Trust in the Lord Jesus Christ.