ויקחו בני אהרן נדב ואביהוא איש מחתתו ויתנו בהן אש וישימו עליה קטורת ויקריבו לפני ד' אש זרה אשר לא צוה ד'
It all boils down to the last four words: Asher lo tzivah Hashem, “That Hashem had not commanded them.” The best laid intentions are of little value if they go against someone’s wishes. In his Sefer Nitzotzos, Horav Yitzchak Hershkovitz, Shlita, gives a practical analogy. Reuven had a good friend, Shimon, whom he had invited to stay at his house whenever he was in the area. Shimon was a welcome guest who would not over-extend his welcome. He would come for a few days, enjoy, and leave. Reuven felt very comfortable inviting Shimon to stay as long as necessary –…