That's the main point of these verses. Christ became the source of eternal salvation for all who obey him. Everything else in these verses explains how Christ could do that. That's where the words dignity , eternity and purity come in. I want to try to show from these verses that Christ became the source of eternal salvation because of his dignity as the Son of God, and because of his eternity in the priestly order of Melchizedek, and because of his purity in the crucible of suffering.
Dignity means worthiness of honor.
That's why nobody gets upset when you poison ants, but would get angry at you if you poisoned all the dogs in the neighborhood. And children have more dignity than dogs, because humans are worthy of more honor than dogs are. The humane society gathers up stray dogs and mercifully puts some of them to sleep. But nobody would let them do that with children. So dignity means worthiness of honor.