Notice that the "promise remains" of entering His rest. This is the subject under discussion. At the time of the writing of Hebrews, the rest had not been attained. Nor has it been attained since. The rest is still in the future. It remains even for Christians today. Paul warns, "lest any of you seem to have come short of it," indicating that though one has received forgiveness, God's Spirit, and gifts of the Spirit, there is still a possibility of falling away. The chance may not be great, but nonetheless, some may fall short of it.
"For indeed the gospel was preached to us as well as to them; but the word which they heard did not profit them, not being mixed with faith in those who heard it" (verse 2). During the time of the Exodus, the people of Israel heard a message of good news from Moses. It consisted of redemption from slavery, the Passover, baptism in the Red Sea, and a journey through the wilderness to the Promised Land. The good news, then, included the occurrences of and the knowledge about all the steps along the way, all of the benchmarks. The purpose for which all those events occurred was the most important part. What good was it to have the death angel pass over their house, for them to receive the forgiveness of sin and redemption from slavery, if they never made it to the Promised Land? That is Paul's warning. The steps, though vital in themselves, are not as important as the goal.
This warning applies especially to today. What Jesus Christ did in His life, in His death, and in His resurrection, is awesome, a wonderful and great gift. It is good news that these things have occurred, but they are not the good news. The good news is the goal, and that has not yet occurred. What Jesus Christ did is exceedingly important to the fulfillment of God's purpose, but it is still possible for us to reject the Son of God even after we have accepted His blood for the forgiveness of our sins, as Hebrews 6, 10, and 12 also show very clearly. So in this analogy, life in, possession of and governance of the Promised Land was the culmination, the good news, the fulfillment—at least physically—of the promises to Abraham.
The message that Jesus Christ brought, the gospel, is about the Kingdom of God, the culmination, the goal, the fulfillment. Certainly it includes the knowledge of and information about those benchmarks along the way, but the Kingdom of God is the goal toward which every Christian is aiming.