וִֽידַעְתֶּם֮ הַיּוֹם֒ כִּ֣י ׀ לֹ֣א אֶת־בְּנֵיכֶ֗ם אֲשֶׁ֤ר לֹֽא־יָדְעוּ֙ וַאֲשֶׁ֣ר לֹא־רָא֔וּ אֶת־מוּסַ֖ר יְהוָ֣ה אֱלֹהֵיכֶ֑ם אֶת־גָּדְל֕וֹ אֶת־יָדוֹ֙ הַחֲזָקָ֔ה וּזְרֹע֖וֹ הַנְּטוּיָֽה׃
И знай этого в этот день; ибо я говорю не с вашими детьми, которые не знали и не видели наказания Господа Бога вашего, величия Его, руки Его могущественной и руки Его протянутой,
Rashi
וידעתם היום AND KNOW YE THIS DAY — Set your heart to know and comprehend, and to accept my reproof.
Chizkuni
ואשר לא ראו את מוסר, “and who have not witnessed Your chastisement;” Moses will furnish the details immediately.
Da'at Zekenim
כי לא את בניכם, “that it was not your children;” Moses warns his own generation that it was they who would be punished for ignoring the laws of the Torah, as it was they who had witnessed G–d’s miracles for them, not their children who had been born in the desert.