As we have already learned (see
Pesahim 100), Rabbi Yehuda and Rabbi Yose differ on how to deal with a situation where a Friday afternoon meal continues into
Shabbat. According to Rabbi Yehuda you must end your meal in order to stop and welcome
Shabbat; Rabbi Yose rules that you can continue your meal.
The discussion on our
daf relates to the cups of wine that must be drunk to close the meal and to welcome the
Shabbat. According to the
baraita we will need two separate cups of wine, a ruling explained by Rav Nahman bar Yitzhak as stemming from the principle
ein osin mitzvot havilot havilot - that we do not perform
mitzvot "in bundles." The idea is that every
mitzva deserves its own focus, and if we try to perform several
mitzvot with the same cup of wine it will be impossible to focus on each
mitzva separately. A similar idea is
ein me'arvin simha be-simha - that we do not combine two joyous occasions (e.g. to have a wedding during
Pesah or
Sukkot), because each one deserves its own focus.
The Gemara distinguishes between a case where we want to combine
Kiddush together with
birkat ha-Mazon (Grace after meals), when this rule would apply, and a case where we need to combine
Kiddush and
havdala (the separation service after
Shabbat or
Yom Tov), like when one of the holidays (
Pesah, Shavu'ot or
Sukkot) falls out on Saturday night and we need to make
havdala to commemorate the end of
Shabbat and
Kiddush to usher in the holiday. In such a case, the Gemara rules that it would be appropriate to use one cup for both ceremonies, since
Kiddush ve-havdala hada milta he - the ceremonies of
Kiddush and
havdala are one and the same, while
Kiddush and
birkat ha-Mazon are two different things.
In explanation of this statement, some
rishonim argue that
Kiddush and
havdala are similar in that they introduce a meal, while
birkat ha-Mazon ends the meal. Others point out that
havdala contains an aspect of
Kiddush in that it serves to emphasize the uniqueness of
Shabbat in distinguishing between
Shabbat and the weekday. Another suggestion that is raised is that, in this case,
Kiddush and
havdala are actually dependent on one another, since the holiday cannot begin until
Shabbat ends. When we announce that
Shabbat is over, we effectively welcome the holiday; when we welcome the holiday we are calling for an end to
Shabbat.
Birkat ha-mazon has no such relationship with
Kiddush at all.