Ray Stedman’s comments on Hebrews 4:14-5:10:

This principle is called in Hebrews “the rest of God,” it is activity out of rest. It is to cease from our self-directed activities, the principle upon which we have lived our human lives ever since we were babies, convinced that we had what it takes to do what we wanted to do, or, at least, could get what it takes from some human source. But this new principle, made available to us only in Jesus Christ, means to cease our self-directed activities and trust in the ability of a second Person to work through us.

That is exactly what faith is. Every one of you has been exercising faith ever since you came into this auditorium; you have been trusting in the work of another person. Though I watched carefully, I did not see a single one of you pick up one of these chairs and examine it to see whether or not it would support you if you sat on it. You took it by faith, you exercised trust in the maker of the chair. Though you do not have the least idea who he is, whether he is a rascal or trustworthy, you have simply taken it for granted and have been exercising a faith which has been supporting you all along. We make faith so difficult, but it is simply trusting in the work of another.

And that is what the life of rest is, trusting in the Lord Jesus who has come to indwell our hearts, to do through us all that we do.