Question: Suppose your non-Jewish business-associate, who lives in the next town over, shows up at your door one fine Yom Tov day, with a live turkey from his farm and a basket of home-grown tomatoes from his garden. Based upon what we learned in our lesson on siman 512, you may certainly ask him to stay for the daytime meal (see there for the reason.) The question now is: Are you all permitted to slaughter the turkey or eat the tomatoes for the meal?
Answer: This scenario is discussed in our present siman, and the Shulchan Aruch and Mishnah Berura identify at least four different halachic issues which affect its ruling. Due to the complexities involved, we will briefly mention the issues and leave it to you - the reader - to watch out for this or similar scenarios in the future.
Issue 1: Melacha. The non-Jew may have performed melachos for the Jew which are not permitted for the Jew to perform himself on Yom Tov. In particular, the melachos of ‘tzod’/trapping or ‘kotzair’/harvesting are not permissible even for food preparation, as we have learned in previous lessons. In general, whatever is forbidden for a Jew to do is forbidden to have a non-Jew do on his behalf.
Issue 2: Muktzah. Since the food was not available to the Jew when Yom Tov began (as it required forbidden melacha to be done in order to make it accessible), it would be muktzah and thus forbidden to be eaten or even handled!
Issue 3: Techumin (boundaries). On both Shabbos and Yom Tov, a Jew is forbidden to walk (i.e. even without carrying) outside of the city limits. Not only is he forbidden to walk to another town, but everything in that town is likewise forbidden to be used by him, since they were outside his ‘techum’ when the day began (even if subsequently the item was brought to him in his town by, say, a non-Jew.) Issue 4: Penalties. In many cases, the Sages ordained a penalty, restricting the use of items obtained through halachic violation of Shabbos or Yom Tov. Sometimes these restrictions are temporary – i.e. throughout the duration of that day of Shabbos or Tov, but lifted once the day is over. Sometimes the restriction lasts into the following night, until enough time has elapsed making it theoretically possible for the particular item to be obtained had one attempted to do so only after the Holy day was over. (Say what?!) For example, suppose the tomatoes were said to be forbidden for the rest of that day of Yom Tov. Suppose that it takes the non-Jewish guest two hours to harvest the tomatoes and deliver them to your house. Halacha might require that you wait until two hours after Yom Tov have passed before eating those tomatoes.
Question: If the non-Jew arrived on the first of a two-day Yom Tov, would that mean two hours after the first day is over or two-hours after the second day is over?)
All these question and more are discussed in siman 515.