I was delighted to be the External Examiner yesterday for a PhD dissertation oral defense yesterday at Andrews University in Michigan. Nice people and I want especially to commend Erhard Gallos. His dissertation explored the possibility of a connection between the sabbath rest of Hebrews 4:9 and the failure of the audience to assemble in Hebrews 10:25. I personally don't see any connection, but he was granted his driver's license and is now free to scholar at will.
While the train of thought of these two chapters is a bit difficult to follow at times, I am at rest with most of my interpretation ;-) First, the lead off is the common warning of Hebrews that if the audience does not endure to the end, they will experience the judgment of God. We have become and remain partakers of the Christ if and only if we are holding firm and hold firm to the end (3:14, 6).
The wilderness generation illustrates this fact. The Israelites left Egypt, but most of them did not enter Canaan because of their failure to continue in faith. They did not enter God's "rest," which in relation to the audience becomes the post judgment existence of believers, the heavenly homeland and better country of Heb. 12.
Hebrews 4 then brings this point home. The audience is like the wilderness generation in the choice they face. They "are entering into rest" like the wilderness generation. What gets confusing is the "now-future" nature of the imagery. The ultimate entrance, given the typology, must be future. But the author also speaks of entering in "every day called 'today'" (4:7; 3:13). Every day, we choose to have faith, so every day we enter into rest.
But the ultimate rest is yet to come. There remains a "sabbath rest" for the people of God (4:9). On that day, we will rest from our works as God rested from his on the seventh day.