2,726. The Volume of a Vow

Hilchos Nedarim 1:4

It is a mitzvah from the Torah for a person to fulfill his oath or his vow, whether it’s a vow prohibiting something or a vow sanctifying something. Deuteronomy 23:24 says, “Observe the statements of your mouth and do as you vowed,” to which Numbers 30:3 adds, “One shall act according to all that he stated with his mouth.”

Hilchos Nedarim 1:5

If a person prohibits himself from eating a certain type of food, such as if he said, “Figs are prohibited to me,” “Figs from country X are prohibited to me,” “These figs are prohibited to me,” etc., he is liable to lashes under Biblical law for eating any amount of them. Numbers 30:3 says, “He shall not desecrate his word” and there’s no minimum volume vis-à-vis a vow. This is because, by virtue of taking a vow not to eat something, it’s as if one stated outright that he wouldn’t eat even the slightest volume. If one said, “It’s prohibited for me to eat the produce of country X” or “for me to eat this fruit,” then he isn’t lashed unless he eats the volume of an olive.