“Let us therefore be diligent to enter that rest, lest anyone fall through following the same example of disobedience.”
In other words, Israel fell from the promised joy of God because of the disobedience of unbelief. And the same thing can happen to any professing Christian. To keep it from happening—and to show that we are more than mere professing Christians—he says, “Be diligent to enter God’s rest”—God’s heaven. Be diligent! Pay close attention to what you’ve heard (2:1); don’t neglect your great salvation (2:3); consider Jesus (3:1); do not harden your hearts (3:8); take care against an unbelieving heart (3:12); exhort one another every day against the deceitfulness of sin (3:14); and FEAR the unbelief that will keep you from your promised rest (4:1).
Do you see the great lesson here? The Christian life is a life of day by day, hour by hour trust in the promises of God to help us and guide us and take care of us and forgive us and bring us into a future of holiness and joy that will satisfy our hearts infinitely more than if we forsake him and put our trust in ourselves or in the promises of this world. And that day by day, hour by hour trust in God’s promises is not automatic. It is the result of daily diligence and it’s the result of proper fear.