Leviticus 16:11-13

11“Aaron shall present the bull as the sin offering for himself and make atonement for himself and for his household (the other priests), and he shall kill the bull as the sin offering for himself.

12He shall take a censer full of burning coals from the [bronze] altar before the Lord, and two handfuls of finely ground sweet incense, and bring it inside the veil [into the Most Holy Place],

13and put the incense on the fire [in the censer] before the Lord, so that the cloud of the incense may cover the mercy seat that is on [the ark of] the Testimony, otherwise he will die.