Nedarim 61: Ending Vows; Signs of Summer

Through a discussion about how to determine when vows will end, the rabbis clarify other important issues.  For example, the rabbis consider whether or not yovel, the Jubilee Year, is included in the first fifty years of the fifty-year cycle (seven cycles of seven years followed by one yovel, Jubilee year) or whether it counts as 'year one' of the upcoming fifty years.  A number of verses from Leviticus 25 are quoted as proofs.  A note shares the halacha: yovel stands on its own.  Thus the last seven-year cycle ends with shemita, which is the 49th year and the Sabbatical year.  Shemita is followed by yovel, the fiftieth year, which is then followed by year one - also thought of as the fifty-first year.

When examining the Mishna's statement about vowing that something is konam until the Passover year, the rabbis consider whether or not it is advisable (or allowed) to put oneself in a state of uncertainty.   A story from Kiddushin 64(b) is used to illustrate this question: a man has two groups of two daughters, one from his deceased wife and one set from his current wife.  He says that he betrothed his older daughter to someone but he does not know which daughter he betrothed - it could be any of the older three, who are each an 'older daughter'.  Rabbi Meir rules that those three daughters are forbidden to marry anyone else due to this uncertainty.

Rabbi Meir believes that a vow lasts until the specified ending event is over.  Rabbi Yosei says that the vow is in effect until that event arrives.  

A new Mishna tells of a vow that forbids something to a person until the grain harvest, or until the grape harvest, or until the olive harvest, the vow is in effect until that date arrives.  The principle is that a time-fixed event ends a vow upon its arrival.    However, if a person vows that s/he is forbidden from something "until it will be [the grain or the grape or the olive harvest]", that vow is valid until the event ends.  And if an event has no fixed time associated with it, then the vow is in effect only until the occasion arrives.

The Mishna goes on to say that if a person says "until the summer (kayitz)", or "until it will be summer" regarding the end of his/her vow, that vow is honoured until the people begin to bring fruit into their homes in baskets.  If s/he says, "Until the summer has passed", however, the vow stays in effect until people put away the knives that cut harvested figs.  Thus a custom helps the rabbis to determine when the summer begins and ends; when a vow begins and ends.

The Gemara argues about figs - how are they actually cut down?  Aren't our fingers enough? And do grapes in the same 'summer fruit' category as figs, or not?  They are also plucked by hand when they are fully ripened.  The Gemara's last comment teaches that most people set aside their fig-cutting knives at the end of summer, though some people do not.

It is amazing that so much of halacha is based on the actual practices of people.  Since we know that this is true, why would we believe that the practices used in antiquity should dictate halacha that applies today, when customs (based on technological, social and physical changes) have altered so dramatically over the years?