The Gemara in Bava Batra (cited by the Gur Aryeh (Devarim 34:5)) records that the final eight pesukim were written בדמע — with tears — and the Maharal there rejects the Ra'em's explanation that this distinction in writing medium was intended merely to mark out those verses for individual Torah reading; rather, the Gur Aryeh (Devarim 34:5–12) insists that the Gemara itself locates the reason precisely in their having been composed through tears, pointing to something intrinsic to those verses as a category apart.
Tiferet Yisrael (ch. 57) explains that prophecy operates only upon things that exist in the prophet's present reality — "the matters that are with him in existence" — and cannot grasp a wholly different world not yet in being, which frames the deeper question of how Moshe could have written about his own death and the events that followed it.
Sifrei Devarim (1:1) underscores that Moshe wrote the entire Torah — "וַיִּכְתֹּב מֹשֶׁה אֶת הַתּוֹרָה הַזֹּאת" — and that "אֵלֶּה הַדְּבָרִים" refers specifically to words of rebuke, implying that Moshe's prophetic voice extended across the whole of the Torah, including its most forward-looking passages.
Derekh Chayyim (3:13) adds that the Masorah — the meticulous tradition of signs preserving every word of the Torah — functions as a fence ensuring the Torah will never be forgotten across generations, grounding the question of the final pesukim within a broader framework of transmission and continuity.