Hebrews 4

Something so divine about the book of Hebrews is the explanation of the "New Covenant" and the comparison of it to the old covenant. This book was written to Israel, so who knew more about the rituals and customs that God ordained by Moses. The old promises that God had made were ready to be done away with at Christs death. Heb 8:13 (In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away.) Israel knows that the law was for the sanctification of their flesh. now this "New Covenant"  was being set in place, and it was made by Christs death, Heb 9:28  (So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation)  This covenant was made open by who received it by faith. So every time the promise or New Covenant is mentioned it is faith based, and only entered into by faith. Heb 4 explains to us the rest that God had promised us, was not entered into because of the lack of faith, or unbelief. Heb 3:19 & 4:11 
19. So we see that they could not enter in because of unbelief. 
11. Let us labour therefore to enter into that rest, lest any man fall after the same example of unbelief.


So let us believe more and more in the solid promise that God has given us. which is a new rest. He has promised us a rest from this world, and has given us a high priest to lead us there. 


Unbelief being our biggest enemy to not being able to receive the promise given to us. I believe that Hebrews makes it clear to us what faith is by explaining it to the ones who were recognized to be having a problem with it. (which was Israel)