cellio | daf bit: Nazir 11

(Today's daf is 12.)

A nazir is forbidden, among things, to consume wine (or grape juice). If a man says: "I declare myself a nazir on the condition that I can drink wine", he becomes a nazir and is forbidden wine -- a condition on a vow can't contradict torah law. If he says "I didn't know that a nazir is forbidden wine", he is still forbidden (but R' Shimon releases him from his vow). If he says "I knew that a nazir is forbidden wine but I thought the sages would give me permission because I cannot do without wine", he is released from his vow (but R' Shimon binds him to it). Why is he released if he thought he would get an exemption? Because we don't hold people to vows broken under pressure. (We accept his claim that he can't live without wine and thus we know he will violate the vow.) (11a-b)