the Day of Atonement: The High Priest Entered Into the Holy Place On
Source: TTT
Leviticus 16:2, 3
And the LORD said to Moses: “Tell your brother Aaron not to enter freely into the Most Holy Place behind the veil in front of the mercy seat on the ark, or else he will die, because I appear in the cloud above the mercy seat. / This is how Aaron is to enter the Holy Place: with a young bull for a sin offering and a ram for a burnt offering.
Hebrews 9:7
But only the high priest entered the second room, and then only once a year, and never without blood, which he offered for himself and for the sins the people had committed in ignorance.