If someone makes a oath/ promise to do or not to do something and they say “for the rest of the week” but they have in mind only until Shabbat–not to include Shabbat itself–is the promise/shevua bound by the plain meaning of the words (to include Shabbat), or by the intent (until Sundown Yom shishi)?
Example…Someone says “I will not eat meat for the rest of the week”, but they really thinking in their heads until Sundown PM Friday so they could eat meat on Shabbat, would the issur be until Shabbat comes in or motzei Shabbat when the week ends?
When someone makes a neder and he stipulates that it should be until then end of that week, it is valid until then end of the coming shabbos. Even though he thought that it should be less than that, he is still bound by what he said, as we say dvarim sh’blev ainom devarim”. He does not have the right to change what he actually said by merely thinking, and since he said it should be until after shabbos then he has to keep it until then. However if he thought that the meaning of the rest of the week means until the end of Friday, then it is will only apply until shabbos. The reason being is that we say that when there is a question of interpretation, (not contradiction), then we go according to the interpretation, and inthis case it goes according to what was meant.
Nedarim 60a, Y:D 320-3, Machaneh Efrayim Nedarim-4, Kol Nidrei 54-13,14.