By Rabbi Chanan Morrison
A careful reading of the text reveals that the Jewish people accepted the Torah at Sinai not once but twice. First it says,
"Moses came and told the people all of God's words and all the laws. The people all responded with a single voice, saying: 'All the words that God spoke - we will do.'" [Ex. 24:3]
And immediately afterwards we read,
"Moses wrote down all of God's words .. He took the book of the covenant and read it to the people. They replied, 'All that God spoke, we will do and we will understand.'" [Ex. 24:4,7]
These two passages cannot refer to the same event. In the first verse, Moses communicated God's words orally, while in the second account he read to them from the sefer habrit.
The Sages taught that there were two Torahs given at Mount Sinai: the Oral Law and the Written Law. The Jewish people first accepted upon themselves the Oral Torah, and afterwards the Written Torah.
Why Two Torahs?
Why was it necessary for the Torah to be given both orally and in writing? Why did the people accept the Oral Torah with the words, "We will do," but when accepting the Written Torah they added, "and we will understand"?
There are two aspects to Torah study. The primary goal of Torah is to know how God expects us to act in the world. This is the purpose of the Oral Law - the Mishnah and the Talmud - which discusses in detail how to apply God's laws to the many diverse situations in life.
The second value of Torah learning is knowledge of the Torah for its own sake. This is the function of the Written Torah. Even if we do not fully understand the words of the Torah, we still fulfill the mitzvah of Torah study. As the Sages taught, "One should always first learn superficially, and later contemplate [what he studied] .. even if one does not fully understand what he has read" [Avodah Zarah 19a].
With the Oral Torah, however, there is no value to its study if it is not properly understood. On the contrary, misunderstanding the Oral Law could lead to mistakes in Halachic rulings and improper conduct.
Attaining clear knowledge of the practical side of Torah level requires a breadth and depth of Torah scholarship. It is unreasonable to expect the entire people to reach such a level of erudition. Therefore, the practical, detailed part of Torah was transmitted orally. Only those who labor in its study, receiving the traditions from the great scholars of the previous generation, will truly merit this knowledge. For if this part of Torah were written down and revealed to all, even unlearned people would feel a false confidence in making legal decisions, despite not having properly studied all of the relevant issues.
One might argue that perhaps the entire Torah should be transmitted orally. But were this the case, Torah knowledge would be limited to only a select few. The Written Torah enables all people to be exposed to Torah on whatever level they are capable of comprehending.
Now we can better understand the Torah's account of Mount Sinai. When accepting the Oral Law, the people responded, na'aseh - "We will do." This aspect of Torah related to the entire people, but only in terms of its practical, Halachic side. It was with regard to the Written Torah, which is intellectually accessible to all on some level, did the people add, venishma - "and we will understand."
First - "We Will Do"
People naturally desire to understand as much as possible, and act according to their understanding. The spiritual greatness of Israel at Mount Sinai was their recognition of the advantage of not writing down the Oral Law, so that their actions would best fulfill God's Will. This is the significance of their response, "We will do": we accept upon ourselves to follow the practical teachings of the scholars and teachers of the Oral Law. Since this acceptance was equally relevant to all, regardless of intellectual capabilities, the verse emphasizes that "the people all responded with a single voice."
Having accepted upon themselves to properly keep the Torah according to the practical dictates of the sages, Moses then presented the Jewish people with the Written Torah. We would have expected that the people would have shown extra affection for the Written Law, since they could approach this Torah directly. But in an act of spiritual nobility, the Jewish people demonstrated their desire to first obey and keep the practical law. Thus they announced, "We will do," and only afterwards, "we will understand."
In summary, the Jewish people received two Torahs at Sinai. Moses first gave them the Oral Law, so they could achieve the Torah's principle goal - proper action in this world. Then Moses transmitted the Written Law, to enable each individual to access Torah at his level, and be prepared to receive the light of the practical Oral Torah.
[adapted from Midbar Shur pp. 160-165]