Parshanut do Liczb 30:24

Shall remain incumbent upon her. In the entire section Scripture uses the language “it will stand” and “her vows shall stand” without saying “upon her,” except here. The reason is because in those cases the vows will exist forever, but here, a widow or divorced woman can have her vow released by a judge if she has regret. Only as long as she does not regret, the vow will stand, and that is why it says “it shall remain incumbent upon her”—as long as she bears the burden of the vow and does not release it.