As we begin Sefer Bereshit, it is unclear what the purpose of this Sefer is. As Rashi, quoting Rebbe Yitzchak, asks, why does the Torah not start with the first Mitzvah in the Torah, “Hachodesh Hazeh Lachem” (Shemot 12:2)? He answers by quoting the Pasuk found in Tehilim “Koach Ma’asav Higid Liamo Latet Lahem Nachlat Goyim” (111:6). The strength of Hashem’s actions in Ma’aseh Bereshit is described in order to give them support for their claims against foreign nations. When other nations claim that Eretz Yisrael is theirs, Bnei Yisrael can simply point to Sefer Bereshit, which clearly shows that Hashem created the world and that He promised to give Eretz Yisrael to Avraham, Yitzchak, and Yaakov.
Rav Moshe Feinstein, in his Sefer Darash Moshe, suggests another answer. He explains that the purpose of Sefer Bereshit is to be a basis for all Mitzvot. He says that a person only fulfills a Mitzvah when he believes that Hashem created everything, because without Emunah the fulfillment of Mitzvot does not matter. Similarly, the Rambam in Hilchot Milachim 8:11 says that only a Nochri who follows the Sheva Mitzvot Bnei Noach because he knows that Hashem commanded Moshe that Nochrim follow them, is considered to be a wise and righteous Nochri. However, a Nochri who just follows the laws without a specific reason is not regarded as such a righteous person. Therefore, in order for Bnei Yisrael to properly fulfill the Mitzvot, they must first recognize and understand that Hashem created the world as described in Sefer Bereshit.
The Chafetz Chaim, in his Peirush on the Torah, gives a similar answer. He quotes a Pasuk from Tehilim, “Ma Gadlu Maasecha Hashem, Miod Amku Machshivotecha” “[Hashem,] Your actions are amazing, and even better are Your thoughts” (92:6). All of Hashem’s creations and Mitzvot have great purpose and meaning, but even more meaningful is the way that these creations act and work. Therefore, the Torah starts with stories of Hashem’s creations and the ways they act so that one can fully understand the basis for the Mitzvot and be able to do what Hashem wants of him.
The basic idea that both Rav Moshe Feinstein and the Chafetz Chaim express is that before one learns something or does something, one must understand what it is he or she is doing, and what the basis is for these actions. However, one question that still remains is why it is so important to understand the basis for the Torah and the Mitzvot; why can’t a person just do the Mitzvot without this whole introduction?
The Vilna Gaon, in his commentary on the Torah, has a beautiful idea that can be used to answer this question. He says that the Torah is our life, and just like the fish cannot live without water, even for a moment, Bnei Yisrael, too cannot live without the Torah. As it says in Devarim 30:20, “…Ki Hu Chayecha Vi’orech Yamecha…” “…because He [Hashem] is your life and your length of days…” The Vilna Gaon also shows how the Torah consists of life’s fundamental ideas that a person uses everyday. Every letter of the word Bereshit represents one of these ideas. The Bet stands for Bitachon or confidence. The Reish stands for Ratzon or desire. The Aleph stands for Ahava or love. The Shin stands for Shtika or silence. The Yud stands for Yirah or fear. Finally, the Taf stands for Torah. These six ideas are the most basic ideas that one uses in everyday life. In addition, Rav Menachem Baker, in his Sefer Parpeparot Latorah, quotes the famous idea of Chazal that the first letter of the Torah is a Bet, and the last letter of the Torah is a Lamed, which combined together spell the word Lev or heart. This again shows how the Torah is our heart, and just as we cannot live or breathe without our heart, so too we can not live without the Torah. Therefore, because the Torah is our life and has all of our life inside of it, it is important to know the background information of the Torah before one begins to practice the Torah. This is the purpose of Sefer Bereshit: to be an introduction to the Torah and all of the principles of the Torah.