Cross reference
Exodus 28:35
35 And it shall be upon Aaron to minister: and the sound thereof shall be heard when he goeth in unto the holy place before Jehovah, and when he cometh out, that he die not.
Leviticus 16:2
2 and Jehovah said unto Moses, Speak unto Aaron thy brother, that he come not at all times into the holy place within the veil, before the mercy-seat which is upon the ark; that he die not: for I will appear in the cloud upon the mercy-seat.
Hebrews 9:12
12 nor yet through the blood of goats and calves, but through his own blood, entered in once for all into the holy place, having obtained eternal redemption.