(א) בקרבתם לפני ה׳ וימותו. אם נפרש שבא להשלמת ספור הסבה שמתו. הרי מיותר תיבת וימותו.
ותו ק׳ מאי וידבר ה׳ והדר ויאמר ה׳.
אלא האי בקרבתם לפני ה׳ וימותו הוא הדבור הראשון. והענין דאע״ג שמתו נו״א בהקריבם אש זרה ולכל תנא כדאית ליה ביומא פ׳ הוציאו לו. בכ״ז לא היו ראוים שימותו מיד. וכי מי שהעובר על חייבי מיתה ב״ש פוגע בו מדה״ד מיד ולמה מתו נו״א מיד ע״ז בא הדבור מפי הגבורה למשה. כי בקרבתם לפני ה׳ וימותו.
משום שחטאם היה בעת שקרבו לפני ה׳ בפלטין של ממה״מ הקב״ה מש״ה פגעו בהם תומ״י מלאכי מות.
ואח״כ אמר ה׳ למשה כל הפ׳ והא שהקדים לה זה הדבור למאמר הפ׳ הוא כדי ללמד לדורות הבאים דבר הנוגע לפ׳ של יוה״כ.
אשר מי שלא יהא נזהר בקטרת לפני ולפנים דמו בראשו וכמו שאירע בבית שני כדאי׳ ביומא די״ט. והיינו משום שפגע בהם עונש בקרבתם לפני ה׳:
When they drew close to the presence of Hashem, and they died: There are two questions to ask about this expression.
Question 1: If we say that this expression is intended to complete the story of why the sons of Aaron, Nadav and Avihu, died (the story begun in Parashat Shemini, back in Chapter 10) then the only piece of information that we are adding to the story is the text "when they drew close to the presence of Hashem", but the words "and they died" are redundant, because we already know from the text in Chapter 10, that they died.
Question 2: Take a look at the first two verses of Parashat Acharei Mot. Why does the first verse say "God spoke..." and immediately after this, the second verse says "God said...".
We can begin to answer these questions by suggesting that God addresses Moshe twice. In the first address, the dibbur, God tells Moshe that Nadav and Avihu died when they drew close to God's presence. This appears to contradict what is taught in the Talmud, on page 53a of the tractate Yoma, which deals with the laws of Yom Kippur. There it is taught that Nadav and Avihu died because they brought a strange fire.
We can resolve this contradiction by explaining that the sin of bringing strange fire does not incur immediate death. If so, why did Nadav and Avihu die immediately? God's first address to Moshe answers this very question. They died at the exact moment that they drew close to the presence of Hashem, and they drew close when they entered the palace of the King of Kings, the Holy One, Blessed Be He. Because of this sin, the angels of death struck them immediately.
Only after He had explained this concept to Moshe, did God begin his second address, the maamar, in which he details the procedure of Yom Kippur.
The reason God does this is to teach future generations a key point related to the Yom Kippur procedure: a High Priest who does not take sufficient care in preparing the incense prior to the Yom Kippur service, puts his life in danger, as we find historically during the Second Temple period. Examples are given in the Talmud, on page 19b of the tractate Yoma. There we find that the same punishment meted out to Nadav and Avihu, was applied to those high priests who did not approach holiness in an appropriate way.