There are many opinions on the author of the book of Hebrews. We believe it was a collaborative effort with Paul and some of his closest companions. Most commentators agree on the time frame of the writing and it would place the writing of Hebrews near the time of Paul's death. In his last recorded letter Paul asks Timothy to bring the scrolls, especially the parchments. Could it be that the parchments had no writing on them and that is what was used to write Hebrews?

Heb 1:3
The Son is the radiance of God's glory (see Genesis 1) and the exact representation of his being, sustaining all things by his powerful word. After he had provided purification for sins, he sat down at the right hand of the Majesty in heaven.
God spoke in the past through the prophets, the Old Testament. Now we have God speaking to us through His Son, the New Testament.

Until we make the "Son" the center of our universe with all our lives revolving around Him, then we fall short of all God wants us to be.

Heb 3:6
But Christ is faithful as a son over God's house. And we are his house, if we hold on to our courage and the hope of which we boast.
Courage and hope are built on the foundation of Jesus. We are His "house" while we sojourn here.

Heb 3:10-13
That is why I was angry with that generation, and I said, 'Their hearts are always going astray, and they have not known my ways.' So I declared on oath in my anger, 'They shall never enter my rest.'" See to it, brothers, that none of you has a sinful, unbelieving heart that turns away from the living God. But encourage one another daily, as long as it is called Today, so that none of you may be hardened by sin's deceitfulness.
The writer(s) or Hebrews tells us that God was angry with the generation of Moses and said that they would never enter His rest. They wandered around for forty years and were not allowed to go into the "Promised Land". If we substitute salvation for rest, we can make the connection that if we do not know His ways, if our hearts go astray, if we have a sinful, unbelieving heart that turns away from God, we will not have His "rest" (salvation).

The "Today" that is mentioned in this passage is the first day of our eternity. Today begins at the moment of our conversion and the indwelling of the Holy Spirit.

Heb 3:19
So we see that they were not able to enter, because of their unbelief.
They don't have salvation, therefore no rest. The gospel was preached to Moses and the others in the desert. The message was of no value to them because they did not combine it with faith.

Heb 4:12
For the word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart.
How is the word of God living and active?

Heb 4:16
Let us then approach the throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need.
We have this confidence in Him not in ourselves. It is approaching the throne without doubt or fear and with respect.

Heb 6:1-2
Therefore let us leave the elementary teachings about Christ and go on to maturity, not laying again the foundation of repentance from acts that lead to death, and of faith in God, instruction about baptisms, the laying on of hands, the resurrection of the dead, and eternal judgment.
As Christians we should have no need of laying again the basic foundations of the faith. We should know the fundamentals. We grow in our understanding of those areas that may be "fuzzy" for us.

Heb 6:7
Land that drinks in the rain often falling on it and that produces a crop useful to those for whom it is farmed receives the blessing of God.
Sounds as if we should drink in the nourishing "rain" and produce a crop of righteousness.
Matt 13:8
Still other seed fell on good soil, where it produced a crop-- a hundred, sixty or thirty times what was sown.