The book of Hebrews was authored by Apollos or Barnabas, both learned Christians.
The book opens in a particularly beautiful description of the great love of God through Christ 1:3 "The Son is the radiance of God's glory and the exact representation of his being, sustaining all things by his powerful word. " In 2:18 human experiences that Jesus had which help Him related to us are mentioned "Because he himself suffered when he was tempted, he is able to help those who are being tempted."
3:12 reminds believers to encourage on another "See to it, brothers, that none of you has a sinful, unbelieving heart that turns away from the living God." Blessings come to those who are spiritually diligent and keep the light of Christ alive and working in their heart, 6:10-12 "God is not unjust; he will not forget your work and the love you have shown him as you have helped his people and continue to help them. We want each of you to show the same diligence to the very end, in order to make your hope sure. We do not want you to become lazy, but to imitate those who through faith and patience inherit what has been promised."
Jesus role as advocate for those who are saved is mentioned in 7:24-25, "but because Jesus lives forever, he has a permanent priesthood. Therefore, he is able to save completely those who come to God through him, because he always lives to intercede for them."
Describing the traditions of sacrifice sins, thanksgiving, etc. and the tabernacle Hebrews 9:11 tells Christians that Jesus covers all of these, describing the new covenant in Christ, "When Christ came as high priest of the good things that are already here he went through the greater and more perfect tabernacle that is not manmade, that is to say, not a part of this creation. He did not enter by means of the blood of goats and bulls and the ashes of a heifer sprinkled on those who are ceremonially clean. How much more, then will the blood of Christ who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from the acts that lead to death so that we may serve the living God!"
Why did Christ have to die: According to 9:22 He satisfied not only many prophesies, but Jewish law as well, "In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness." 11:6 speaks of the commendation that God has for those who seek the truth, "And without faith it is impossible to please God, because anyone who comes to him must believe he exists and that he rewards those who earnestly seek him."