(16:1) God spoke to Moses right after the death of Aaron's two sons who brought an unauthorized offering before God and died.
right after the death Why is their death mentioned in connection with Yom Kippur? To teach that just as Yom Kippur atones for the Jewish people, so does the death of the righteous provide atonement for the Jewish people (Jerusalem Talmud, Yoma 1:1).
(16:13) There, before God, in the holy of holies, he shall place the incense upon the fire, so that the smoke from the incense cover the ark-cover over the tablets of the testimony. Then He will not die.
There, before God, in the Holy of Holies, he shall place the incense upon the fire This tells us that he should not prepare the incense outside and then bring it in—as opposed to the view of the Sadducees, who said that he must prepare the incense outside and then bring it in (Yoma 53a).
NOTE: The Sadducees were a heretical sect that rejected the Oral Torah. They denied the immortality of the soul, bodily resurrection after death, and they did not believe in punishment