Musar על סוכה 55:6

When Moses refers to G–d having "arrived from Sinai" (33,2), he refers to an event which occurred on the third day of the week, i.e. the numerical value of the word בא in this verse is 3. You will now understand why the Torah commences with the letter ב as a symbol of blessing. There is an interesting Aggadah in the Otiyot d'Rabbi Akiva: They asked the letter ב who had created it, whereupon the letter pointed at the letter א with its עוקץ, the "sting" projecting from the right side of the bottom of this letter. It is a fact that when the Torah was actually given to the Jewish people, i.e. when G–d revealed Himself by means of communicating the Ten Commandments, these commandments commenced with the letter א i.e. אנכי ה' אלוקיך. This shows that the letter א is the true root of blessing. This root is אור, light, the original light which was concealed from this earth at the time Adam sinned in Paradise. We quoted the Midrash as saying that the world was created for the sake of Torah which is called ראשית; we may deduce that the letter ב preceding this word is a reference to the two Torahs, i.e. the written and the oral Torah. These two Torahs may also be meant when the Torah reported the creation of the "two great luminaries, the great luminary and the small luminary" (Genesis 1,16). The "great" luminary would be the מעשה מרכבה, the esoterics, as expressed by the written Torah which is a combination of letters of the Holy Name of G–d; the "small" luminary would refer to what the Talmud describes as the הויות של אביי ורבא, the discussions exploring the oral law which were carried on by such Talmudic giants as Abbaye and Rava. The written Torah is symbolized by the letter א, the great light which nowadays is kept hidden and which contains the secrets called "the soul of souls" (Zohar on פרשת בהעלותך). These secrets will remain hidden till such distant future when Man too will be able to wear the garments made of אור, light -as had been the case before the sin- and to benefit from this great light. Nowadays, when we are forced to make do with כתנות עור, garments made of hide, i.e. a corrupt form of "light" spelled with the letter ע, we must be content with "only" seventy facets of the written Torah, i.e. with the letter ע symbolizing the light of the written Torah. Once our world will be filled with knowledge of G–d as envisaged by Isaiah 11,9 this letter ע will be replaced by the mystical dimension of עין, "eye." At that time all the hidden secrets which no human eye has ever beheld will be revealed. Why does the "sting" of the letter ב point at the letter א? Because the oral Torah [being merely based on unwritten tradition. Ed.] is always at pains to demonstrate its validity by establishing a link with the written Torah. The relationship of the oral to the written Torah is similar to the relationship between the first woman and the first man, about which Adam said: כי מאיש לוקחה זאת, "for she has been detached from Man" (Genesis 2,23). The oral Torah is perceived of as having been derived from the written Torah. The relationship of איש to אשה is the same as the relationship of זה וזאת; hence the relationship of the written Torah to the oral Torah is as the relationship of זה to Tת. Oral Torah in fact has its origin in the written Torah. This is the reason why the Talmud keeps raising the question: מנלן, i.e. "where is the source for this teaching in the written Torah?" The word אור appears five times in the story of creation. This alludes to the five books comprising the written Torah.