Chapter 4 begins with “let us therefore.” “Therefore” refers back to lessons from Israel in chapter 3. Israel had “an evil heart of unbelief in departing from the living God” (3:12). The nation could have entered “the promised land” soon after receiving the Law. They could have rested. But because ten Israelite spies reported, “We can't attack those people; they are stronger than we are.” (Numbers 13:31, NIV), Israel was condemned to wander in the wilderness for 40 years.
Paul is comparing this to the life of the Christian. Israel failed because of a lack of faith, but we are instructed to have full faith. We are to trust God’s provisions in Christ for our forgiveness of sins. “We which believe do enter into rest.” (verse 3)
Hebrews 4:3 continues “they shall enter into my rest although the works were finished from the foundation of the world.” God’s plan for a redeemer was conceived and arranged before the foundation of the world. (Revelation 13:8) God’s rest is the complete peace He has because He has turned the work of redemption and restoration into the hands of His worthy Son. (Revelation 5)
But how could God rest when He sees humankind in such a mess? God’s ultimate purpose will be accomplished. “So shall my word be that goes forth out of my mouth, it shall not return unto me void but it shall accomplish that which I please and it shall prosper in the thing whereto I sent it.” (Isaiah 55:11)
His ultimate purpose is beautifully and briefly summarized in Ephesians 1:9, 10 (Weymouth). “He made known to us the secret of His will. And this is in harmony with God's merciful purpose for the government of the world when the times are ripe for it–the purpose which He has cherished in His own mind of restoring the whole creation to find its one Head in Christ; yes, things in Heaven and things on earth, to find their one Head in Him.”
Christians enter God’s rest when we lay aside our own works and have faith in Jesus’s work (past, present, and future). Hebrews 4:9-10 (NIV), “There remains, then, a Sabbath-rest for the people of God; for anyone who enters God’s rest also rests from their works, just as God did from his.” Our fullest rest will be in heaven. But to go to heaven, we need to work to deny our wills to do God’s will (verse 11). If we keep an honest heart, we will see where we fall short (verse 12) We can’t hide our sins from God. He sees us as we really are. (verse 13)
Jesus is our High Priest who sympathizes with us. (verse 15). “Let us, therefore, come boldly to the throne of grace, that we may obtain mercy and find grace to help in time of need,” Hebrews 4:16 (NKJV). There, we will receive help every time we need it. No matter how often this may be. (verse 16)