Chazal tell us that the mitzvah of קדושים תהיו was said at a gathering of all Klal Yisrael. Perhaps one can suggest that the significance of this context, is to explain the environment
The famous story is told in the Midrash (Vayikra Rabbah) about a pedlar who travelled around the neighbourhood of Tzippori, offering for sale the elixir of life. From his study, Rebbi Yanai heard the pedlar proclaiming: מאן בעי סם חיים “who wants the potion for eternal life? Rebbi Yanai asked him for a sample. The pedlar refused saying “People like you do not need it”. After much importuning however, he consented to show it R’Yannai. He took out a book of Psalms and, opening it, pointed to the text: מי האיש החפץ חיים ... נצור לשונך מרע ... סור מרע וגו’ “Who is the man who desires life?... guard your tongue from evil…” on seeing this R’Yannai exclaimed: כל ימי הייתי קורא פסוק זה ולא הייתי יודע היכן הוא פשוט עד שבא רוכל זה והודיע מי האיש החפץ חיים “All my years I have read this verse without knowing the simple explanation of the words, and now this pedlar has shown me their meaning.”
The above interpretation needs clarification. Nadav and Avihu brought a Korbon when they weren’t commanded to. How can the Ohr HaChaim say it was not a punishment? They made what seems an obvious mistake; they brought an Aish Zorah - an alien fire, as the Passuk (10:1) tells us.