Taken from Pastor Chuck Smith’s Bible study in Hebrews 4

Unbelief keeps you from all that God has and desires for you. It is unbelief that keeps you back. Now, the unbelief so often stems from our looking at ourselves and seeing our failures, our shortcomings, our weaknesses. Because somehow we cannot divorce our minds from the reward of the good, positive enforcement. You reward the child for good behavior. And the child is punished for bad behavior. And somehow we cannot divorce our minds from this concept. We have a tendency to carry it over unto God. And we think of God rewarding our good behavior. And when we are conscious of our bad behavior, there is no expectation or anticipation of God blessing us.

In fact, we say, well, I know that God can’t bless me because I failed in this or I did that or I yelled at the kids or I, you know, got angry at that fellow who cut me off on the freeway. So I know that God can’t bless me. And with that attitude, I don’t have faith to receive the blessings of God; hence I don’t enter in to all that God has for me.

And so that’s basically the warning here. God has much more for us, but He doesn’t give it to us as a reward for our good behavior, He gives it to us because He just loves us! And you know to accept grace, gracefully, is a very difficult lesson to learn.

When God begins to bless me, though I realize I don’t deserve it, I then try to promise God. Well, Lord, I’m going to do better and I will deserve it! I mean I’ll prove that You did a good thing in blessing me like that and I’ll be better! And yet, I can’t just get my mind free, totally, from the idea that the reward for good behavior, rather than God just loving me and by His grace, wanting to bless me, if I’ll just simply trust Him and believe Him to do it.

So, they did not enter in because of unbelief! That’s what kept them out. They did not believe that God would do the things that He promised to do; and hence, they failed to enter into that rest.