Chapter 87:19
Animals on Shabbos
19. It is permissible to invite a Gentile to eat in one's home on Shabbos;
the Sages prohibited doing so on Yom Tov, only because they were concerned
that one may cook extra food for him (1); on Shabbos, however, this is of
no concern, [since it is forbidden to cook].
It is permissible to provide food on Shabbos for a Gentile, even though he
is not dependent on you for his food supply; since the halacha mandates
that one provide food for Gentiles (regardless of their financial status),
in order to maintain peaceful relations ("darchei shalom"), it is
considered as if one is responsible to feed him ("mezonosav olecha") (2).
FOOTNOTES:
(1) It is permissible to cook on Yom Tov; this applies to food that one
will need on Yom Tov itself, however, one may not cook food on Yom Tov for
the sake of a post-Yom Tov meal. When one is cooking food for Yom Tov, one
may cook more than one needs in order to have left overs after Yom Tov;
this is true only if it can all be achieved with the same act, for example,
by merely adding extra pieces of meat to the pot.
It is only permissible to cook on Yom Tov for the sake of a Jew, but not
for a Gentile (Shulchan Aruch 512:1); although it would be Biblically
permissible to increase, on behalf of a Gentile, the amount of what is
already being cooked for a Jew (as per previous paragraph), the Sages
prohibited doing so, due to a concern that one might cook extra food for
the Gentile alone. Furthermore, the Sages prohibited even inviting a
Gentile to a Yom Tov meal, because people might end up cooking extra food
specifically on behalf of the Gentile guest.
(2) And therefore, it is not considered an unnecessary burden ("Tircha
Shelo LeTzorech"), which is prohibited on Shabbos. See HY 82:9 for the
halachos of how to give food to a Gentile on Shabbos without coming to
violate Shabbos prohibitions.