If you asked an Old Testament believer "where is the most holy place on Earth?" they would have instantly replied "the Holy of Holies in the temple in Jerusalem. That is where God himself manifests his presence between the cherubim on the Ark of the Covenant." If you further asked "can you visit it? Is it possible to go there to meet with God, or even to have a look" the answer would have been shock. "Of course you can't go there, no way, absolutely not. You would be obliterated by holy glory of God. One person gets to go there, under conditions strictly laid down by God. He can't go whenever he likes, he goes once a year when God says."
Which makes the climax to the main argument of Hebrews incomprehensibly mind-blowing for an Old Covenant believer to hear. If you are familiar with it, it is likely you no longer hear the seismic shock of what our writer has been building up to:
Therefore, brothers, since we have confidence to enter the Most Holy Place by the blood of Jesus... 10:19
Stop right there, let it wash over you. Let it sink in. For the original hearers it was the biggest imaginable paradigm shift, the most revolutionary challenge of all time to their worldview.
Christians can come to the very presence of God, into the presence of that previously-obliterating holy glory, with confidence!
Sometimes I meet Christians who, sadly, haven't yet grasped how great a blessing is theirs. "I couldn't come. I'm not worthy to meet God" sounds humble when in fact it is sub-Christian. Anyone who feels this about themselves is not yet walking fully in biblical Christianity. The reason I can say that is that they have obviously not processed what Hebrews has been impressing on us: that their consciences are now clean towards God because of Jesus; that they have an eternal salvation with a Great High Priest who has brought them eternal redemption; that their sins are really, really forgiven; that Jesus - their Great High Priest - wants them to come. I hope anyone who hears this then wants to come themselves, with great joy. If they still don't something is badly wrong.