2 and Yahweh said to Moses, "Tell Aaron your brother not to come at just any time into the Most Holy Place within the veil, before the mercy seat which is on the ark; lest he die; for I will appear in the cloud on the mercy seat.
12 He shall take a censer full of coals of fire from off the altar before Yahweh, and two handfuls of sweet incense beaten small, and bring it within the veil. 13 He shall put the incense on the fire before Yahweh, that the cloud of the incense may cover the mercy seat that is on the covenant, so that he will not die. 14 He shall take some of the blood of the bull, and sprinkle it with his finger on the mercy seat on the east; and before the mercy seat he shall sprinkle some of the blood with his finger seven times.
15 "Then he shall kill the goat of the sin offering that is for the people, and bring his blood within the veil, and do with his blood as he did with the blood of the bull, and sprinkle it on the mercy seat and before the mercy seat.
34 "This shall be an everlasting statute for you, to make atonement for the children of Israel once in the year because of all their sins."
It was done as Yahweh commanded Moses.