Hebrews 3 is a Big Shock Chapter for its original recipients. It has been where everything in the book has been building to so far, and everything else in Hebrews flows out of it. Chapter 3 demands a complete reorientation of mind for its first audience: they trusted Moses, they considered themselves "in Moses", they thought that Moses was the high point of the nation's relationship with God and the revelation of God through Moses was the highest, clearest and most important words that would ever be communicated from God. Moses, Moses, Moses.
Our writer's argument is:
Jesus is greater that Old Testament prophets (of which Moses was the supreme one)
Jesus is superior to angels (who mediated the Law to Moses)
Therefore Jesus is greater than Moses (and, he will go on to say, greater than the Law of Moses)
Put yourself in their shoes. They had been taught for 1400 years that following Moses and obeying the Law was the exclusive way to know and be accepted by God. No Moses, no relationship with God. This is a HUGE claim that Hebrews 3 is making.
Read more9 Observations from Acts 13:13-52
Paul says we can now be justified from everything that could not be justified by the Law of Moses. It is a VITAL point. Let anyone who thinks that Christians now relate to God through the Spirit being given to help us obey the Law of Moses take note - there were things that it never justified. It is now fulfilled and superseded by the forgiveness of sins in Jesus. This is the point of all evangelistic preaching. We don't do it to Gentiles in the same way as to Jews, but the goal is the same - turn to Jesus not religion (or anything else) to get your sins forgiven
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