“And he shall make atonement for the holy place, because of the uncleannesses of the children of Israel, and because of their transgressions, even all their sins, and so shall he do for the tent of meeting, which dwells with them in the midst of their uncleannesses.”
And the purpose of all this is to make atonement for the holy place because it has been polluted by the uncleannesses of the children of Israel (as depicted in the previous five Chapter s) and also because of their transgressions and their sins revealed by consideration of the Law, both evil doings and evil thoughts. Thus on this day is the pollution removed from the holy tent of meeting which is dwelling with them in their uncleannesses.
This special Day above all days is in order to allow the dwellingplace of God to be able to still continue to dwell among them, by dealing with all their uncleannesses and their sins which have affected it. The holiness of God is such that even with all the precautions for the prevention of the defilement of that holy place, they have not been enough. But on this Day He will remedy that by these ceremonies, despatching the uncleannesses and the sins into the far off wilderness. It is because this will be done on the Day of Atonement that He can deal so lightly with their uncleannesses during the year.
But these were all but shadows until He should come Who would in Himself fulfil all this and more, making a way open for ever into the full presence of God for all who are in Him. He would enter but once and remain there for ever, for His sacrifice was eternally complete, and nothing else remained to be done. It was a completed and eternal work.