The incident of mai merivah is one of the most obscure narratives of the Torah. The Ohr Hachaim Hakadosh cites ten different positions, from Rashi to the Maasei Hashem, as to what the sin of Moshe was. Rashi (Bamidbar 20:12) explains the sin to have been Moshe's hitting the rock instead of speaking to it. The Ramban challenges Rashi by asking, if Moshe was to only speak to the rock, why was he told to take the staff? Moreover, asks the Netziv (Bamidbar 20), we are not informed as to what exactly Moshe was to say to the rock.
The Netziv then suggests that mai merivah has to be viewed from the context as to when it occurred. In his hashlama to the book of Bamidbar he postulates that the book is one of transition from the time the Jewish people entered the midbar to the time they are about to enter Eretz Yisroel. It is a book of transition from a state of l'malah min hatevah - from mon, be'air and clouds of glory, to a state of tevah, a natural world of man working the land and dependent upon rain for his water supply.
It is for this reason explains the Netziv that thirty nine years prior to mai merivah, at Massah U'merivah (Shemos 17:1-7) Hashem actually instructs Moshe to hit the rock. The mateh - staff of Moshe - personifies a miraculous existence. We recount at the Pesach seder the verse from parshas Ki Tavo (26:8) "Hashem took us out of Egypt with a strong hand ... with signs and with wonders." The haggadah explains - "os-os, zu hamateh - 'signs' refers to the staff of Moshe". Thus, at the infancy of the Jewish nation the rapport between Hashem and the former slaves was supernatural. Now as they are about to enter Eretz Yisroel, Hashem wants to teach them what the procedure will be in case of a drought. The mishna (Ta'anis 2:1) teaches that they would bring out the ark to the town square, and the eldest among would preach ways of inspiration. This was to be the new method, the new rapport between the nation and Hashem. Moshe, explains the Netziv, due to his anger, forgot this approach and relied upon the former proven method of hitting the rock, which is why Moshe believed he had the staff in the first place, if the new method did not succeed.
The Ohr Hachaim suggests a different approach, citing a medrash (Yalkut, parshas Chukas #764) which says that Moshe was instructed by Hashem, "Teach before it one chapter", meaning, learn Torah before the rock, and nature will respond positively on behalf of Torah. That nature is subservient to Torah, as is understood by our Chazal - "Breishis" for Israel, who are called "reishis", did Hashem create heaven and earth. The ideal harmony between nature and Israel is that nature is to serve Israel's needs. Thus the Ohr Hachaim explains that the significance of the splitting of the Red Sea was not so much the actual parting of the waters, but rater the timing of the event. He notes (Shemos 14:24) that the water split for Rav Pinchas ben Yair (Chulin 7a). He had the merit of Torah, so it is understandable that the water should divide. However, at Yam Suf they had not yet received the Torah, and still the water split! This was indeed a miracle!
While much of mai merivah is couched in mystery, one concept emerges mist clearly. The world was created to sustain the Jewish people and the study of Torah. Often we marvel at the ability of young kollel families to make ends meet. The response to that wonderment is that of the Yalkut - "sha-neh alov perek echad" - one mishna, one daf of gemorrah, one siman of Shulchan Aruch, has positive consequences beyond our national comprehension.