The phrase "fell dead" means to suddenly die. AT: "suddenly died before Yahweh" (See: [[rc://en/ta/man/translate/figs-idiom]])
# before Yahweh
This refers to Yahweh's presence, meaning that Yahweh saw everything that happened. AT: "in Yahweh's presence" (See: [[rc://en/ta/man/translate/figs-metonymy]])
# they offered to him unacceptable fire
Here the word "fire" is used to refer to "burning incense." AT: "they burned an incense offering in a way that Yahweh did not approve of" (See: [[rc://en/ta/man/translate/figs-metonymy]])