וִֽידַעְתֶּם֮ הַיּוֹם֒ כִּ֣י ׀ לֹ֣א אֶת־בְּנֵיכֶ֗ם אֲשֶׁ֤ר לֹֽא־יָדְעוּ֙ וַאֲשֶׁ֣ר לֹא־רָא֔וּ אֶת־מוּסַ֖ר יְהוָ֣ה אֱלֹהֵיכֶ֑ם אֶת־גָּדְל֕וֹ אֶת־יָדוֹ֙ הַחֲזָקָ֔ה וּזְרֹע֖וֹ הַנְּטוּיָֽה׃
At alamin ninyo sa araw na ito — sapagkat hindi ang inyong mga anak ang kinakausap ko, sila na hindi nakaalam at hindi nakakita ng pagdidisiplina ng Walang-Hanggan na inyong Diyos, ng Kanyang kadakilaan, ng Kanyang makapangyarihang kamay, at ng Kanyang nakaunat na bisig,
Shemirat HaLashon
And, (in my humble opinion,) it is possible to answer that Moses' saying "They will not believe me" may have led some to come to doubt his prophecy, as in the episode of Korach. [For, although in the end, the truth of his prophecy was evident to all — as it is written (Devarim 11:2): "For it is not [with] your children [that I speak now], who did not know and who did not see the chastisement of the L-rd your G-d… (6): And what He wrought against Dathan and Aviram, the son of Eliav… (9): …but with you, whose eyes have seen the entire great deed of the L-rd, that He has wrought" — still, in the beginning, he suffered sorely at the hands of Korach, Dathan, and Aviram.