This is a very complex chapter to read, and perhaps it is particularly complex in our King James Version, and that is inevitable because the King James Version so closely hugs the Greek original to seek to do justice to it. Modern versions may tidy it up a little for smoother reading, but there's always something lost on the way, and if we can only hold back and be patient with our old version, it is actually the most accurate and most carefully translated.
Because of their upbringing in Judaism the Jewish converts were in danger of feeling the lack of an ongoing priesthood. For the believer, Christ is now our great high priest, far better, far higher than all the high priests that there ever were on earth. He is the true high priest, and yet they were used to the Levitical priesthood, and so they were vulnerable to people called the Judaizers. These people tried to turn the true converts back to the Jewish law and the Jewish ceremonial. ‘Oh,’ we can imagine them saying, ‘so you think there is no priesthood, do you, that all the centuries of Levitical priests are banished and we have no need of them? And you think that there are no more sacrifices, and so you Christian people think that none of the sacrifices made in time past by our priests were actually effectual? You think that they didn't cleanse a single person from sin, is that what you say?’ Yes, that is what the Christian preachers said. That is the teaching of the New Testament: that all the Old Testament sacrifices were just visual aids. Forgiveness was given on account of that future atonement that would come with the Messiah, and all the sacrifices only pointed to it and illustrated it. ‘But no,’ said the Judaizers, ‘those sacrifices were effective and valid, they actually took away sin. The apostles were quite wrong in saying otherwise.’ Here in the reasoning of this chapter the legitimacy of Christ as the only mediator, the only true priest, is set forth.