The writer is saying that Israel's entering into Canaan under Joshua was a partial and temporary entering of rest given by God (Jos 21:44, 22:4). However, it was not the end of entering into rest given by God, as he states (v.1), for God continues the invitation in Ps 95:7-8.
God still gives rest. . .through faith in his Son, where the believer--like God who rested from his work of creation--also ceases his efforts to gain salvation by his own works and rests in the finished work of Christ on the cross, and which spiritual rest now will be completed in our final rest (Rev 14:13).
So which verses are you talking about that he quotes--v.3 and v.7?
v.3 - The writer warns the Hebrew Christians not to fall short of the promise of the gospel through lack of faith, as Israel had done. His argument, as he sometimes does, is from the opposite--as God has sworn that unbelievers shall not enter his rest (3:11, 4:3), so those who are not shut out by unbelief will enter in, if God invites them in (Ps 95:7-8).
v.7 - God set another day, today, the day of the divine grace of the gospel, to invite men again into his rest, which the writer warns the Hebrew Christians not to set their hearts against.