Our Gemara on Amud Beis references a particular phrase used in the Torah, “זה הדבר” “ this is the word“, or possibly, “this is the thing“. When the Torah uses a phrase like that, it implies a kind of specificity that is used for various derashos.
Rashi (Bamidbar 30:2) quotes a Sifrei that discusses this terminology and how it applies to the prophecy of Moshe:
זה הדבר. מֹשֶׁה נִתְנַבֵּא בְּ”כֹה אָמַר ה’ כַּחֲצֹת הַלַּיְלָה” (שמות י”א) וְהַנְּבִיאִים נִתְנַבְּאוּ בְּ”כֹה אָמַר ה'”, מוּסָף עֲלֵיהֶם מֹשֶׁה שֶׁנִּתְנַבֵּא בִּלְשׁוֹן “זֶה הַדָּבָר”.
זה הדבר THIS IS THE WORD — Moshe prophesied with the words (introduced his message by the statement), “Thus saith the Lord, About midnight [will I go into the midst of Egypt]” (Exodus 11:4), and other prophets also prophesied with “Thus saith the Lord”, Moses, however, had an additional superiority in that he prophesied also with the expression “This is the actual word [that God hath spoken]” (Sifrei Bamidbar 153:2).
So the phrase, “zeh hadavar” implies an exclusive form of clarity and communication that only Moshe achieved, above the other prophets. The Mizrachi explains, that this speaks to a difference in the content and purpose of the prophecy itself. Other prophets are speaking in terms of reaction with current events. Meaning to say, in light of whatever is occurring now, the prophet has a message from God about what to do right now. This is encoded in the phrase “thus said Hashem” “כה אמר ה׳”. This is what Hashem wants you to do right now. However, Moshe’s prophecy included timeless and universal truths and principles, that is why only he can be a law giver. His statements are not always just reactions to current events, but enduring principles and ideas that must be applied universally, and continuously. That is represented in the phrase, “this is the word” “ זה הדבר”. This is not merely a reaction to something going on now, but the final word and idea that must be understood and taken to heart universally.