How can a Ger Toshav be obligated to observe Shabbos? A Ger Toshav is a Nochri, not a
Jew, and the Gemara (Sanhedrin 58b) clearly states that a Nochri who rests from
Melachah on Shabbos is Chayav Misah!
(a) RASHI writes that a Nochri who accepts upon himself to observe the seven Mitzvos
of Noach and not to serve Avodah Zarah is also required to keep Shabbos, because the
desecration of Shabbos is compared to Avodah Zarah.
TOSFOS asks that the Gemara in Sanhedrin clearly implies otherwise. The Acharonim
(ARUCH LA'NER) explain that, according to Rashi, the Gemara in Sanhedrin is referring
only to a Nochri who is involved in worshipping Avodah Zarah. Such a Nochri is indeed
Chayav Misah if he rests from Melachah on Shabbos. However, once he accepts upon
himself not to serve Avodah Zarah, he must observe Shabbos.
(b) TOSFOS (DH Zeh) explains that a Ger Toshav has no obligation to observe Shabbos.
Rather, the Gemara is saying that the obligation of a Ger Toshav is akin to that of
an Eved -- a Jew is not allowed to have an Eved, or a Ger Toshav, do Melachah for him
on Shabbos (Rashi himself says this with regard to an Eved, in DH Bein
ha'Shemashos).
Why did Rashi explain the obligation of a Ger Toshav differently than Tosfos?
Rashi did not want to explain like Tosfos, because a Ger Toshav is different than an
Eved in that a Ger Toshav is not subject to any Jew. Thus the verse cannot be telling
us that we are not allowed to tell him to do Melachah, because he has no imperative
to listen to what we tell him anyway! If he decides to do the Melachah, it is as if
he is deciding to do it on his own accord, and there is no Isur d'Oraisa for a Nochri
to do Melachah for a Jew. Therefore, it must be that the Torah is telling *him* not
to do Melachah, and not that it is telling *us* not to ask him to do Melachah for
us.
(c) The TOSFOS YESHANIM explains that this Ger Toshav is actually a Ger Tzedek who is
in the process of converting. If Shabbos arrives before he has completed his Gerus
(similar to the case of an Eved that Rebbi Akiva discusses earlier), he must observe
that Shabbos. Since he had intention to convert, he is not considered a Nochri
anymore with regard to the prohibition against keeping Shabbos, and thus he must rest
from Melachah on Shabbos.