For we do enter into the rest, we who have believed ( οἱ πιστεύσαντες, the historical aorist, pointing to the time when Christians became believers; with a reference also to τῇ πίστει in the preceding verse: but the emphasis is on the first word in the sentence, εἰσερχόμεθα: "For we Christian believers have an entrance into the rest intended") even as he hath said, As I sware in my wrath, If they shall enter into my rest; although the works were finished from the foundation of the world. This seems to be a concise enunciation of the proof, unfolded in the verses that follow, of the true rest being one into which Christians have still an entrance. The idea is that, though God's own rest had been from the beginning, and man had not yet entered it, yet the possibility of his doing so had not ceased to be intimated: it had continued open potentially to man.
For he hath said somewhere ( που cf. Hebrews 2:6) of the seventh day on this wise, And God rested the seventh day from all his works; and in this place again, If they shall enter into my rest. Here the argument is carried out. The first passage quoted shows what must be understood by the "rest of God;" the second shows that it still remains open, that "it remaineth that some should enter thereinto." This being the case—
Since therefore it remains that some should enter into it, and they to whom the good tidings were before preached entered not in because of disobedience, he again defineth a certain day, saying in David, after so long a time, Today; as it hath been before said, Today, if ye will hear his voice, etc. The continued openness of the rest, and the failure of the Israelites of old to enter it, are the reasons why a further day for entering was defined in the psalm. But here the thought is suggested that the Israelites had not finally failed, for that, though those under Moses did so, the next generation under Joshua did attain the promised laud. No, it is replied; the rest of the promised land was but a type after all; it was not the true rest of God: otherwise the psalmist could not have still assigned a day for entering it so long after the arrival at Shiloh;—
For if Joshua had given them rest, he would not have spoken afterward of another day. The conclusion is now drawn: There remaineth therefore a sabbath rest for the people of God; the true nature of the rest intended being beautifully denoted by the word σαββατισμὸς, which refers to the Divine rest "from the foundation of the world," while the offer of it to true believers always, and not to the Israelites only, is intimated by the phrase, "the people of God."