Parashas Acharei Mos · Passuk 16:13
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim.
English: “And he shall not die” — implying that if he does not do so [cover the kapores with the cloud], he dies.
Cloud is me’akev for life
The covering cloud of incense is essential; without it the entry is fatal.