Leviticus 16:2

16:2 and the Lord said to Moses: “Tell Aaron your brother that he must not enter at any time into the holy place inside the veil-canopy in front of the atonement plate that is on the ark so that he may not die, for I will appear in the cloud over the atonement plate.

Hebrews 9:12

9:12 and he entered once for all into the most holy place not by the blood of goats and calves but by his own blood, and so he himself secured eternal redemption.