It is prohibited on Yom Tov to do melacha (either Biblically or Rabbinically prohibited) specifically for the sake of a non-Jew (even a non-Jewish employee.) The Rabbis forbade even “increasing the amount” (i.e. making larger quantities) for the sake of a non-Jew (Ed. See MBY 503:1-2 Preparing food on Yom Tov for the next day.) The Rabbis further forbade inviting a non-Jew for the Yom Tov meal. This decree was enacted out of concern that one might cook an extra pot of food specifically on behalf of the non-Jewish guest. (Ed. The decree does not apply to a Yom Tov meal which coincides with Shabbos!)
Exceptions to this decree include the following:
- If a non-Jew enters one’s home uninvited, one may serve him a meal, provided that one’s entire meal has been prepared.
- It is permitted to send cooked food to the home of a non-Jew, provided that the Jew does not cook anything extra for this purpose, and he does not carry the food where there is no Eruv. (Ed. See – we need an Eruv even on Yom Tov!)
- In a situation where ones refusal to serve food or extend an invitation to a non-Jew may lead to animosity, it is permitted to add an extra measure to the pot which one cooks for himself or other Jews and serve it to the non-Jew, or to invite him for a Yom Tov meal.
In a similar vein, it is prohibited to do any melacha specifically for the sake of an animal. However, adding an extra measure for its sake is permitted.