The Pasuk in Parashat Nitzavim states that on the day of Moshe’s death, “VaYichtov Moshe Et HaShirah HaZot BaYom HaHu,” “Moshe wrote this song on that day” (Devarim 31:22). Chazal interpret this to mean that Moshe wrote the entire Torah, spanning from the beginning of Bereishit to the end of Devarim, on the day of his death. Another opinion states that, in fact, Moshe wrote 13 different Torah scrolls: one for each of the twelve Shevatim and one more which was placed in the Aron. Since this is physically impossible for one human to achieve in one day, Chazal say that this was a miracle. But what exactly was the purpose of this miracle?
The Alshich explains that the miracle was intended to teach an important lesson to Bnei Yisrael about not ranking Mitzvot. Bnei Yisrael might have been tempted to claim that the Aseret HaDibrot were the only important Mitzvot because only they were written BeEtzba Elokim, “with the Finger of God.” The miracle that took place on Moshe’s last living day proves otherwise. Moshe was unable to write 13 Torah scrolls in one day; Hashem must have helped him with it. Therefore, it becomes obvious that every Mitzvah is from Hashem, and that every Mitzvah must be performed properly and treated with respect.