Parallel
Hebrews 3:19
Patriarchal Greek New Testament (1904) · Berean Standard Bible
καὶ βλέπομεν ὅτι οὐκ ἠδυνήθησαν εἰσελθεῖν δι᾽ ἀπιστίαν.
So we see that it was because of their unbelief that they were unable to enter.