What was the nature of their sin? For millennia, commentaries have discussed and debated the inner meaning of the text. If the Torah chose to honor Moshe by suppressing the details of his sin, the result was the opposite: All manner of accusations have been hurled at Moshe and Aharon to explain the harsh punishment they received. ...
In a sense, the Israelites had been lulled into a false sense of security. As they moved from one disaster to the next, Moshe was always there to put out fires. Together with his brother Aharon, Moshe had guided the nation from slavery to freedom, from Mount Sinai to the cusp of the Land of Israel. There had been murmurings, dissent, and even a full-scale rebellion along the way, but the leadership team of Moshe and Aharon, had always been there to avert disaster and expertly guide the people. And then, quite suddenly, out of the blue, we are informed that their leadership, and their very lives, will be coming to an end.
Painting the story in broad strokes is easy: It begins with one of the Israelites’ countless complaints, in this case, about water. A miraculous solution is presented, -- and then, the unexpected: A death sentence is handed down. What had changed? Why was this incident different from all the others? Why this doom, death and disaster now?
The text itself is enigmatic:
God spoke to Moshe, saying, 'Take the staff, and you and Aharon assemble the community. Speak to the rock in their presence, and it will give forth its water…' Moshe took the staff from before God as he had been instructed. Moshe and Aharon then assembled the congregation before the rock. 'Listen now, you rebels!' shouted Moshe. 'Shall we produce water for you from this rock?' With that, Moshe raised his hand, and struck the rock twice with his staff. A huge amount of water gushed out, and the community and their animals were able to drink. God said to Moshe and Aharon, 'You did not have enough faith in Me to sanctify Me in the presence of the Israelites! Therefore, you shall not bring this assembly to the land that I have given you.' These are the Waters of Dispute (Mei Merivah) where the Israelites disputed with God, and where He was sanctified. (B’midbar 20:7-12)
What was their mistake? At what point had Moshe and Aharon displayed a lack of faith? What was the nature of their sin? For millennia, commentaries have discussed and debated the inner meaning of the text. If the Torah chose to honor Moshe by suppressing the details of his sin, the result was the opposite: All manner of accusations have been hurled at Moshe and Aharon to explain the harsh punishment they received. Was it Moshe’s anger (which is not explicitly mentioned in the text)? Did he implement God’s instructions imprecisely? Or was it something else?
Context may be important: This week’s parasha opens with the law of the red heifer. The ashes of this heifer are used as an antidote to the ritual impurity generated by death. Rashi comments on the very particular term used to describe this law:
This is the statute of the Torah: Because Satan and the nations of the world taunt Israel, saying, “What is this commandment, and what purpose does it have?” Therefore, the Torah uses the term “statute –(chok),” [as if to say,] I have decreed it; you have no right to challenge it. (Rashi B’midbar 19:2)
A chok, Rashi explains, is a law whose logic is elusive, a statute we must accept unquestioningly in a “leap of faith.” These types of laws often torture us; they cause us to question ourselves, our reason, even our sanity. Generally, Rashi’s comment (which, in turn, is based on a rabbinic position) is understood as being directed toward the illogical or even paradoxical nature of this particular ritual: The person who was ritually impure “magically” becomes pure when sprinkled with the ashes of the red heifer, while the person who actually prepared the potion becomes impure.
However, Rashi may not be addressing the inner contradiction of the red heifer ritual at all. In fact, it is hardly likely that the “nations of the world” would have been the least bit surprised by a ritual potion that has seemingly magical properties: The entire world of idolatry was involved in the occult. The only thing which may have troubled pagan onlookers - or given them cause to mock this ritual - was the fact that even the Jews adhered to practices that have no logical basis.
As for us, something much deeper torments us in this parasha, a paradox more profound than that of the red heifer ritual: death itself. The mystery of death is the impenetrable thing that lies at the heart of this ritual and is its impetus. It is not the impurity and subsequent purity that challenges our powers of reasoning and tortures our minds; it is the inescapable, inexorable fact that people die.
The death sentence issued against Moshe and Aharon is not arbitrarily placed in this parasha; this broader context is part of the message: Their deaths are part of this greater mystery. God’s rebuke may well be a tantalizing hint at this greater context: Moshe and Aharon failed to lead the people to a level of faith that would have solved this great mystery once and for all, failed to elevate the people to the level of spiritual enlightenment that would have relegated death itself to the past. Moshe’s death, then, remains as much a mystery as any and every other death. We search the text for a clue to Moshe’s sin, in vain. Indeed. in the closing verses of the Torah, we are told that Moshe’s death will forever remain shrouded in mystery:
…And no person knows the place of his burial, unto this day. (D’varim 34:6)
Perhaps Parashat Chukat teaches us that the mystery is not only the place of Moshe’s burial, but the cause of his death as well. Just as no human being knows, has known, or ever will know where Moshe is buried, so, too, does the “reason” for his death - like every other death - remain unknowable. 
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