Charles Ellicott Commentary Deuteronomy 29:14-15

"Neither with you only do I make this covenant and this oath, but with him that standeth here with us this day before Jehovah our God, and also with him that is not here with us this day" — Deuteronomy 29:14-15 (ASV)

Neither with you only ... but ... also with him that is not here with us this day — that is, “also with generations yet to be” (Rashi).