daf bit: Nedarim 53

[cellio]

The mishna teaches: he who vows abstinence from wine is permitted apple-wine (cider); if from oil he is permitted sesame oil; if from honey he is permitted date-honey; if from vinegar he is permitted vinegar made from winter grapes; if from vegetables he is permitted wild vegetables, all because it is a "qualifying epithet". That is, "wine" defaults to grapes and if we mean something else like "apple-wine" we add a qualifying word. But then the g'mara clarifies by way of an example: in a place where sesame oil and olive oil are both used, sesame oil is forbidden to him despite this mishna, because it's prevalent enough that he might have meant to include it too. From this we learn that a doubtful prohibition is resolved stringently. (53a)