The Parshah of Acharei Mos opens, “G-d spoke to Moshe after the death of Aharon’s two sons, when they drew near before G-d and they died.” The wording of this verse seems unnecessarily repetitive. Having established that this was taking place “after the death of the sons of Aharon,” and explaining the circumstances in which they died—“when they drew near to G-d”—why repeat “and they died”?
According to an interpretation offered by Ohr Hachaim regarding the cause of Nadav and Avihu’s death, the words “and they died” can be understood not as repeating the fact that they died, but explaining why they died.
Nadav and Avihu died “by the kiss of G-d,” says Ohr Hachaim. He explains this to mean that they sensed and delighted in the closeness of G-d to the point that their souls expired from sheer ecstasy.
Chassidus explains, however, that Nadav and Avihu’s demise under such circumstances is regarded as sinful. Granted, a Jew must aspire to transcend the constraints of physicality in unbridled devotion to G-d, but at the same time it is imperative to acknowledge that G-d grants us physical life because He desires that we transform this physical world into a place where His presence is manifest. Our ultimate objective must therefore be not to escape mortal life, but to remain within and sanctify it. In contrast, the conduct of Nadav and Avihu, who allowed their spiritual rapture to reach a point of no return, is regarded as a “sin.”
This is the meaning of the verse “After the death of the two sons of Aharon, when they drew near before G-d and they died.” What brought about the death? Why was their conduct displeasing to G-d? Because “they drew near before G-d and they died” — i.e., they opted to delight in the closeness to G-d, to love G-d to death quite literally, at the expense of fulfilling their mission to infuse holiness into mortal life.
—Likkutei Sichos, vol. 3, pp. 987–988