“Rav Yehudah says in the name of Rav, where do we learn that [the obligation to] recite a blessing prior [to learning Torah] is biblical? As it is written (Deuteronomy 32:3), ‘When I proclaim Hashem’s Name, ascribe greatness to our God’” (Berachot 21a). The interpretation of this verse is that the entire Torah is comprised of the names of HaKadosh Baruch Hu (Zohar, part 2, 87:1; Tikunei Zohar, Tikun 10) for He is completely concealed from us, and through the Torah HaKadosh Baruch Hu is revealed to the world. Hence, we learn that the Torah is the names of HaKadosh Baruch Hu and through it He is manifest. That is the meaning of the verse, “Ki Shem Hashem ekra,” “When I proclaim Hashem’s Name” – before learning Torah, “Havu godel l’Elokeinu,” “Ascribe Greatness to our God” – recite a blessing for the Giver of the Torah.
In practice, the Rishonim are divided concerning the question of whether these words should be taken literally, making the recital of Birkot HaTorah before learning a biblical commandment. According to the Rambam and the Shulchan Aruch (Orach Chaim 209:3), reciting Birkot HaTorah is a rabbinic enactment and what Chazal extrapolated from the verse is none other than an asmachta (a reference). Based on this, in a case of doubt, one must be lenient and refrain from reciting the blessings, and that is the custom of the Sephardim (Kaf HaChaim 47:2). According to the majority of Rishonim, among them the Ramban and the Rashba, the source for the mitzvah to recite Birkot HaTorah is biblical. Therefore, when a person is uncertain as to whether or not he recited Birkot HaTorah, he must be stringent and recite them, in keeping with the rule, sefeika d’oraita l’chumra (we are stringent concerning matters of biblical uncertainty), and that is the minhag of the Ashkenazim (Mishnah Berurah 47:1).
However, all opinions agree that if there is a person present who did not yet recite Birkot HaTorah, it is preferable to fulfill one’s obligation by hearing him recite them and in that way avoid uncertainty. When there is no such option, if one is about to pray and recite Ahavat Olam (or Ahavah Rabbah), he should have kavanah to fulfill his obligation of Birkot HaTorah in his recital of that berachah. Nevertheless, if the time to pray has not yet arrived, and there is no one whom he can hear recite the berachot, according to those who maintain that the obligation to recite Birkot HaTorah is biblical, he must be stringent and recite them out of uncertainty. It is sufficient to recite only the third berachah, “Asher bachar banu” (“Who chose us,”) for it is the most important from among Birkot HaTorah.