This weeks Parsha relates one of the most difficult stories which took place in the Midbar. With Bnei Yisroel complaining about the lack of water after the death of Miriam, Hashem instructs Moshe to “speak” to the rock and it would yield water. (Chukas 20:8) Instead, Moshe Rabbeinu “strikes” the rock. The rock does in fact yield water but Hashem tells Moshe that on account of his not “believing in him”, he would not be Zoche to lead Bnei Yisroel into Eretz Yisroel. (20:12) This leaves us to deal with the age old question – How could Moshe Rabbeinu hit the rock. Why on this singular occasion did he deviate from Hashem’s instruction?
In order to properly answer this question, it is helpful to understand some basic tenets of the Rambam. The Rambam teaches that every Midda a person should have in moderation, not too little not too much. As an example, the Rambam states that even generosity can be had in too great a quantity where one would give everything he has to others and be left with nothing to eat. The Rambam cites his conviction about moderation in many other contexts as well. (See the Rambam’s discourse on the Shemoneh Parakim as well as numerous references contained in Hilchos Daus). Curiously, the Rambam makes one very specific exception to his rule of moderation. This exception is with respect to the mida of Ka’as – Anger. The Rambam states that this mida one should not have at all, not even in moderation. The Rambam explains that anger causes people to lose control of one’s self and can cause them to say and do things that they do not mean. In effect, he describes anger as allowing us to do things out of character since at that moment we are not in complete control of ourselves.
With this Rambam, we can begin to understand what may have caused Moshe Rabbeinu to be Nichshal this one time. In the Pasuk after Hashem instructs Moshe how to deal with the outcry from B’nei Yisroel, Moshe picks up his Mateh and says to B’nei Yisroel, “Shimu Na Hamorim – listen to me you rebels!!”. He then proceeds to strike the rock. (20:10) In that one moment, whether out of frustration for the repeated rebellions by B’nei Yisroel or something else, Moshe Rabbeinu got angry. He scalds B’nei Yisroel as “rebels” as he prepares to once again demonstrate Hashem’s majesty. Even Moshe Rabbeinu, in a moment of justified anger, did something he was not told to do.
It’s no wonder that the Rambam places this mida by itself in solitary confinement. As he states, no good can come from it. When one considers the ramifications of anger, it is painfully obvious how damaging it can be, with no redeeming benefits. In our parsha, it was a solitary act, but it also can cause us to say something in a moment of reduced self control where the damage can be long lasting. The wrong thing spoken in a fit of anger can cause long term hurt to another and can never really be taken back. If we learn this lesson from this week’s Parsha, we can understand in practicality the Rambam’s instruction to avoid this most dangerous Mida.
 The Rambam even discusses how the mida of jealousy can be a good thing if one is jealous of someone else’s Torah knowledge and uses that to motivate himself to learn more.