Albert Barnes Presbyterian @notesbybarnes

Verse 9. There remaineth, therefore, a rest. This is the conclusion to which the apostle comes. The meaning is this, that according to the Scriptures there is now a promise of rest made to the people of God. It did not pertain merely to those who were called to go to the promised land, nor to those who lived in the time of David, but...

Matthew Henry Presbyterian @wholebiblehenry

Here, I. The apostle declares that our privileges by Christ under the gospel are not only as great, but greater than those enjoyed under the Mosaic law. He specifies this, that we have a promise left us of entering into his rest; that is, of entering into a covenant-relation to Christ, and a state of communion with God through Christ, and of growing up therein...

Commenting on Hebrews 4:1-10

Jamieson-Fausset-Brown Reformed @jfbcommentary

therefore--because God "speaks of another day" (see on Heb 4:8). remaineth--still to be realized hereafter by the "some (who) must enter therein" (Heb 4:6), that is, "the people of God," the true Israel who shall enter into God's rest ("My rest," Heb 4:3). God's rest was a Sabbatism; so also will ours be.