Hebrews 4:6-8
“Seeing therefore it remains” (he says) “that some must enter therein, and they to whom it was first preached entered not in because of unbelief: again he limits a certain day, saying in David, Today, after so long a time; as it has been said before.” But what is it that he means? “Seeing then” (he means) that “some must” certainly “enter in,” and “they did not enter in.” And that an entrance is proclaimed, and that “some must enter in,” let us hear from what this is clear. Because after so many years (he says) David again says: “Today if you will hear His voice, harden not your hearts”, “For if Joshua had given them rest he would not afterward have spoken of another day.” It is evident, that he says these things, as of persons who are to attain some recompense.
Source: Homilies on the Epistle to the Hebrews (New Advent)