Leviticus 16:13

and 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 .

He is to put the incense on the fire before the Lord, and the smoke of the incense will conceal the atonement cover above the tablets of the covenant law, so that he will not die.

And he shall put the incense upon the fire before the Lord, that the cloud of the incense may cover the mercy seat that is upon the testimony, that he die not: