Parshas Haazinu, is known as the “song of testimony”; the song that carries with it the testimony of the Jewish people’s observance of G-d’s commandments and the effects of the lack of this observance. There is an ancient tradition of memorizing the Song of Haazinu. The verse states, “And now you shall write this song [of Haazinu], and you shall teach it to Bnei Yisrael; place it in their mouths [memorize it].” From here, we learn that the Jewish people in the times of Moshe were commanded to learn this song by heart. This tradition of memorizing Parshas Haazinu has continued throughout the generations, as written by Gedolei Yisrael. What is so unique about this Parsha, that of all the Parshiyos we find that specifically this Parsha is to be committed to memory? The answer is that this Parsha contains hidden messages intended for each Jew’s service of Hashem. In this Mamar, the Alter Rebbe defines the message conveyed by Moshe to the Jewish people in the opening verses of the song. Encrypted within this verse is a wealth of background behind the power of Torah and Mitzvos and how this power is activated; the relationship between the animal and G-dly souls, and how they all correlate to bring about the revelation of G-dliness in this world below. This message is given by Moshe to all types of Jews, including both the “Heaven Jew” and the “Earth Jew”, the Jew that is occupied solely with Torah learning and the Jew that works hard to provide a living for his family. Both Jews can and must exert themselves in their service of G-d, as explained in this Mamar.
 This tradition is not recorded in any classical sources of previous times [other than in the verse mentioned above and the Sichos below, which record it in the name of the Maharal and the Maggid of Mezritch] and was seemingly an oral tradition. Many schools have a tradition of learning it by heart. Vetzrauch Iyun Gadol as to why the Poskim or Mefarshim on the verse, ibid, make no mention of this tradition for the generations after. See footnotes below.
 Vayeilech 31/19
 Rashi ibid.
 Even Ezra ibid; Rasag ibid.
 Seemingly, however, this commandment only applies to that generation, and hence we do not find that every Jew is taught Haazinu by heart, and it is simply viewed as a good Segula. Furthermore, perhaps one can say that the commandment was only for Moshe to teach it to them until they memorized it, and it was not a commandment for the Jewish people even in that generation to learn it, and certainly not in later generations, although it is still a Segula still remains. This requires further study.
 The Maharal of Prague stated that one is to recite the Parsha of Haazinu by heart each day, and that doing so brings success and long life. [Sefer Hazichronos 1/29] The Baal Shem Tov directed Rav Chaim Rappaport of Lvov to recite the song of Haazinu by heart during his famous journey. [Sefer Hazichronos 1/139 English edition] The Maggid of Mezritch stated that the song of Haazinu is to be memorized [by the masses]. [Sefer Hasichos 1944 p. 136-138; Sefer Hatoldos Hamaharash [of Rebbe] p. 74] The learning of the song of Haazinu – each person is required to know it by heart and doing so brings great blessing. The Rebbe Rayatz stated, “I heard from Gedolim that every Jew is required to know the song of Haazinu by heart. If the businessmen only knew of the great blessing that the recital of Haazinu from memory can bring to their business, they would be a lot more careful in this.” [Sefer Hasichos 1941 p. 46, Hebrew edition]