A. Let us therefore: This phrase, or this idea, appears repeatedly in the Book of Hebrews. A doctrinal truth is presented – in this case, the truth of a remaining rest available by faith – then the truth is applied.
B. Be diligent to enter that rest: The rest is there, but God does not force it upon us. We must enter that rest. Clearly, the rest is entered by faith; but it takes diligent faith. This shows us that faith is not passive; it takes diligence to trust in, rely on, and cling to Jesus and His work for us.
C. Lest anyone fall according to the same example of disobedience: If we are not diligent to enter that rest, the result can be a disaster. We may fall according to the same example of disobedience. We may fall, even as the children of Israel did in the wilderness.
Based on the Enduring Word Bible Commentary by David Guzik.