Parashas Nitzavim · Passuk from filename
Torah Temimah points to Torah Temimah citation.
English: There is room for conditions in vows, but not in oaths... Just as the future generations have no mental reservation in their hearts, so too you have no mental reservation in your hearts.
Custom (A distinction between neder and shevuah derived from the inclusion of future generations, who clearly cannot have attached private conditions.)
Because the covenant binds even those not yet born — who cannot possibly have made a mental condition — the same must be true of those who stood there. An oath of this kind admits no private reservation. The brit is absolute.