The holy sefer Divrei Torah by the saintly Minchas Elazar of Munkatch, zt”l (8th edition, 35), explains why this specific Torah portion was chosen: “Because Parashas Tetzaveh always coincides with the seventh of Adar, the day of Moshe’ passing. In a leap year the parashah falls on the seventh of Adar Rishon—which is considered the primary seventh Adar.”
He adds that we find a similar phenomenon with other great tzaddikim. In the parashahs corresponding to their passing, their writings contain few or no original insights, serving as a subtle allusion to their deaths. For example, the holy sefer Noam Elimelech does not include discourses on Parashas Vayakhel, the parashah in which he passed away. Instead, the discources are placed later, at the end of Parashas Pekudei, as noted in Ohel Elimelech (siman 289). This pattern is also evident in the passing of other great tzaddikim, such as Rav Tzvi Elimelech of Dinov, author of Bnei Yissaschar, and Rav Tzvi Hirsch of Zidichov, author of Ateres Tzvi. Who can understand such holy and profound mysteries?
The deeper reasoning for this phenomenon of Moshe is explained in the holy sefarim. In Moshe’s statement (Shemos 32:32), וְ עַ תָּ ה אִם תִּשָּׂא חַטָּאתָם וְאִם אַיִן מְחֵנִי נָא מִסִּפְרְ ךָ אֲשֶׁר כָּתָבְתָּ - And now, if You will forgive their sin, (good); but if not, erase me, please, from the book that You have written, Moshe demonstrated unparalleled messirus nefesh for the sake of Israel’s welfare and salvation. He offered himself entirely as their atonement, even at the cost of being erased from the Torah and losing his eternal remembrance. This self-sacrifice signified complete devotion, as being cut off from the Torah would have been as if Moshe had never existed.
Similarly, Moshe’s passing on the seventh of Adar represents absolute messirus nefesh for the benefit of Klal Yisrael. It is known that Moshe prayed 515 prayers (the gematriya of ואתחנן, Devarim 3:23) to enter Eretz Yisrael. But this was denied him, and in his premature death, he gave up his life for Yisrael, ensuring that Divine wrath would be directed at inanimate objects (the Beis Hamikdash) rather than the living people of Yisrael, for had he built the Beis Hamikdash, it would have been so holy that it could never have been destroyed. So it is with the death of other tzaddikim who are mosser nefesh for the Jewish people that their death atones for everyone (Moed Katan 28a).
This error led the wicked Haman to rejoice when his lot fell in the month of Adar, believing it auspicious because Moshe passed away in that month (Megillah 13b). However, he did not realize that Moshe was also born in Adar, and that even Moshe’s passing in this month reflected his messirus nefesh for Yisrael’s salvation. This act served as a merit for Israel, turning the month from sorrow into joy.
The Baal HaTurim comments
“Moshe’s name is not mentioned in this parashah, unlike every other parashah from the time of Moshe’s birth. The reason is that Moshe said (Shemos 32:32), וְאִם אַיִן מְחֵנִי נָא מִסִּפְרְךָ אֲשֶׁר כָּתָבְתָּ - Erase me, please, from the book that You have written, and the curse of a chacham, even when conditional, takes effect (Makkos 11a). This was fulfilled here.” This idea is also mentioned in the Zohar Hakadosh (3:246a).
