He's addressing perseverance in the Christian life, not how to attain salvation. Some people were considering a return to the animal sacrifices of the old covenant, but if Christ's sacrifice wasn't enough to atone for all sins, no other sacrifice would be enough either. Christ's work is sufficient to atone for all sins. People cannot be repeatedly lost and saved. They're either saved once and forever or they aren't saved at all.
Nobody actually loses salvation.
The point is that if salvation wasn't secure in Christ, it wouldn't be secure anywhere. Looking for salvation in a return to animal sacrifices is hopeless, as is looking for salvation through works. Nobody is justified, then goes to Hell. No, he doesn't. Faith without works is dead in the sense that true faith results in works.