Nedarim

The Master said: 'And just as in other vows, he who does not fulfil them violates the injunctions, he shall not break his wad, and thou shalt not delay to pay it, so in neziroth.' Now, as for 'he shall not break his word' as applying to [ordinary] vows, it is well: it is possible e.g., if one says, 'I vow to eat this loaf', and does not eat it; he violates the injunction, 'he shall not break his word'. But how is, 'he shall not break [his word],' possible in the case of neziroth.? For, as soon as one says, 'Behold, I am a nazir' he is one; if he eats [grapes], he is liable for, nor eat moist drapes or dried;  if he drinks [wine], he violates, he … shall drink no vinegar of wine, or vinegar of strong drink, neither shall he drink any liquor of grapes.  — Raba answered: It is to transgress two [injunctions].  How is 'thou shalt not delay to pay it,' referring to neziroth, conceivable? [For] as soon as one says 'Behold, I am a nazir', he is one; if he eats [grapes], he transgresses, 'neither' shall he … eat moist grapes or dried?' — When one says: 'when I wish, I will be a nazir'.  But if he says, 'when I wish', the injunction 'thou shalt not delay' does not apply?  — Said Raba: E.g., if he says, 'I must not depart this world before having been a nazir,' for he becomes a nazir from that moment.  For this is similar to one who says to his wife: 'Here is your divorce, [to take effect] one hour before my death,' where she is immediately forbidden to eat terumah.  Thus we see that we fear  that he may die at any moment: so here  too, he becomes a nazir immediately, for we say, Perchance he will die now.