Following this illuminating path, we will now explain the connection between the mitzvah of Tzitzis and the mitzvah of Shabbas. In the special middle berachah of all the tefilos we recite on Shabbas, we say: "וטהר לבנו לעבדך באמת"—and purify our hearts to serve You truthfully. Now, the Torah always refers to the day of Shabbas as "יום השביעי"—the seventh day. For example, in the Aseres HaDibros, it says (Shemos 20, 8): "זכור את יום השבת לקדשו, ששת ימים תעבוד ועשית כל מלאכתך ויום השביעי שבת לה' אלקיך"—remember the Shabbas day to sanctify it. Six days shall you work and accomplish all your work; but the seventh day is Shabbas to Hashem.
In this context, the sixteen weekly “aliyot” to the Torah are completed on Shabbas. Similarly, the offering of the sixteen lambs—commencing on the first day of the week—is completed on Shabbas. Thus, the ל"ב acts of kedushah related to “amud haTorah” and “amud ha’avodah” are completed on Shabbas Kodesh. As explained, they possess the wonderful ability to sanctify the ל"ב—heart—of a Jew. For this reason, in all of our tefilos on Shabbas, we recite the words: "וטהר לבנו לעבדך באמת"—and purify our hearts to serve You truthfully.
Yetzer Tov and Yetzer Hara in the Heart
Let us elaborate based on a Midrash (Bamidbar Rabbah 22, 9) related to the passuk (Koheles 10, 2): "לב חכם לימינו, זה יצר טוב שהוא נתון בימינו, ולב כסיל לשמאלו, זה יצר הרע שנתון בשמאלו". “The heart of a wise man is to his right,” refers to the yetzer tov, which has been placed on his right side, while “the heart of a fool is on his left,” refers to the yetzer hara, which has been placed on his left. This teaches us what the author of the Tanya discusses at length in Likutei Amarim (9): The yetzer hatov is located in the right cavity of the heart, and the yetzer hara is located in the left cavity of the heart. This is the implication of what Chazal expounded (Berachos 54a) on the passuk (Devarim 6, 4): "ואהבת את ה' אלקיך בכל לבבך וגו', בשני יצריך ביצר טוב וביצר הרע." “And you shall love Hashem, your G-d, with all your heart, etc.” “With all your heart” (both cavities) means with both of your yetzers—with the yetzer tov and the yetzer hara.
