Leviticus 16:2

16:2 and the Lord said to Moses: “Tell Aaron your brother that he must not enter at any time into the holy place inside the veil-canopy in front of the atonement plate that is on the ark so that he may not die, for I will appear in the cloud over the atonement plate.

Leviticus 16:13

16:13 He must then put the incense on the fire before the Lord, and the cloud of incense will cover the atonement plate which is above the ark of the testimony, so that he will not die.