Theophylact of Bulgaria
After so long a time David again says, "Do not harden your hearts," like the fathers who did not enter because of unbelief. He gives us grounds to infer the opposite, that we shall enter if we believe. Clearly this is the future rest, and it awaits us.
For David surely was not speaking about Palestine, since they already possessed it then. Nor was the discourse about the seventh day, for that existed from the creation of the world. Therefore there exists a certain third rest, the Kingdom of Heaven, into which the true Jesus and faith in Him lead us.