After so long a time — It was above four hundred years from the time of Moses and Joshua to David. As it was said before — St. Paul here refers to the text he had just cited.
Related Commentaries of Hebrews 4:7
Hebrews 4:7
7 Again, he limiteth a certain day, saying in David, To day, after so long a time; as it is said, To day if ye will hear his voice, harden not your hearts.