כִּי֩ אֶת־אֲשֶׁ֨ר יֶשְׁנ֜וֹ פֹּ֗ה עִמָּ֙נוּ֙ עֹמֵ֣ד הַיּ֔וֹם לִפְנֵ֖י יְהוָ֣ה אֱלֹהֵ֑ינוּ וְאֵ֨ת אֲשֶׁ֥ר אֵינֶ֛נּוּ פֹּ֖ה עִמָּ֥נוּ הַיּֽוֹם׃
נײַערט אי מיט דעם װאָס שטײט דאָ מיט אונדז הײַנט פֿאַר ה׳ אונדזער גאָט, אי מיט דעם װאָס איז דאָ ניט פֿאַראַן מיט אונדז הײַנט.
Rashi
ואת אשר איננו פה [NOT WITH YOU ALONE DO I MAKE THIS COVENANT … BUT WITH HIM THAT STANDETH HERE …] AND ALSO WITH HIM THAT IS NOT HERE — i.e. with the generations that will be in future (i.e. Moses is not referring to persons who happened to be absent from the assembly, for it states, v. 10, that all were present: “You are standing this day all of you before the Lord”) (Midrash Tanchuma, Nitzavim 3).
Ramban
AND ALSO WITH HIM THAT IS NOT WITH US THIS DAY — “that is, also with the future generations.