וִֽידַעְתֶּם֮ הַיּוֹם֒ כִּ֣י ׀ לֹ֣א אֶת־בְּנֵיכֶ֗ם אֲשֶׁ֤ר לֹֽא־יָדְעוּ֙ וַאֲשֶׁ֣ר לֹא־רָא֔וּ אֶת־מוּסַ֖ר יְהוָ֣ה אֱלֹהֵיכֶ֑ם אֶת־גָּדְל֕וֹ אֶת־יָדוֹ֙ הַחֲזָקָ֔ה וּזְרֹע֖וֹ הַנְּטוּיָֽה׃
你們今日要明白——我不是對你們的兒女說話，他們不曾知道，也不曾看見永恆者你們的上帝的管教、祂的偉大、祂大能的手和伸出來的膀臂，
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.