Leviticus 16:11-13

11"Aaron shall present the bull as a sin offering for himself, and shall make atonement for himself and for his house. He shall kill the bull as a sin offering for himself.

12And he shall take a censer full of coals of fire from the altar before the Lord, and two handfuls of sweet incense beaten small, and he shall bring it inside the veil

13and put the incense on the fire before the Lord, that the cloud of the incense may cover the mercy seat that is over the testimony, so that he does not die.