Musar על חגיגה 28:19

When he had said "the G–d of my father has come to my assistance" (Exodus 18,4), he implied that even his father Amram had become so refined and purified that he qualified as an איש האלוקים. The words "He has saved me from the sword of Pharaoh," in addition to "the G–d of my father came to my help," mean that just as one grants additional wisdom to those who already possess a degree of wisdom, so Moses, seeing he had already possessed basic qualifications, advanced to even higher rank both spiritually and physically, so that even Pharaoh's sword could not harm his neck anymore than it could harm a pillar of marble. This is a hint that marble is incapable of becoming ritually impure. When the four sages entered the פרדס, i.e. the study of esoterics, מעשה מרכבה, Rabbi Akiva warned his colleagues "when you see pure marble, do not say "water, water!" (Chagigah 14)

This is why the Torah in 16,1 did not write בהקריבם, "when they brought close (their offering)" but בקרבתם לפני ה', when they came close to G–d. This "coming close" was of a spiritual, conceptual nature. Their death was an example of what the Psalmist meant when he said: "The death of His pious ones is something very precious to the Lord" (Psalms 116,15). Rabbi Abraham Saba, author of the Tzror Hamor, in his commentary on Genesis 13,5 already wrote that the experience of Nadav and Avihu paralleled the four sages – of whom Rabbi Akiva was one – who נכנסו לפרדס, entered the orchard, [euphemism for study of the mystical aspects of Torah. Ed]. The four were Rabbi Akiva, Ben Azzai, Ben Zoma and Elisha ben Avuyah (who emerged as an heretic). These four sages had already been preceded by Adam, Noach, Abraham and now the two sons of Aaron in their desire to probe the mysteries of the מעשה מרכבה. The word פרדס used in this story related in Chagigah 14 means a place in which grapes and pomegranates grow. Adam sinned regarding both the נגלה, revealed aspect of Torah legislation, as well as against the נסתר, hidden aspect of G–d's commandments. The Talmud describes him as קצץ בנטיעות, having mutilated the young saplings in the garden of religion, and having turned into an heretic. The same thing happened to his counterpart Elisha ben Avuyah. Noach too drank from the wine, became drunk, and as a result temporarily of unsound mind. Ben Zoma reportedly beheld something he was not spiritually prepared to understand and as a result suffered insanity.

The Talmud reports in Chagigah 14b that four outstanding scholars entered the "orchard," i.e. they investigated secrets, mystical dimensions of Torah study not given to everyone to understand. Only one of these four sages, Rabbi Akiva, returned from this investigation without any harm. Four people preceded these four Talmudic scholars in their desire to probe these mysteries. They were: Adam, Noach, Abraham and the sons of Aaron (who are considered as one, as a team). They all entered this "orchard" or vineyard.