98:1 Any labor that may not be performed on Shabbos may likewise not be performed on yom tov. Just as on Shabbos we may not have such labor performed for us by a non-Jew, so too on yom tov. Just as we must have our animals rest on Shabbos, so too on yom tov. (Rema 246:3 disagrees about the need to have animals rest on yom tov but the practice is to be stringent in this matter. See Mishnah Brurah 246:19.) The only difference between Shabbos and yom tov is regarding food. The Torah tells us (Exodus 12:16), “except for that which every person must eat, that alone may be done by you.” This includes kneading, baking, slaughtering, cooking, carrying and lighting a fire (from an existing source, as we will see in 98:31). These actions are permitted on yom tov even when not for food but for another purpose. This is a tradition received the Sages (Talmud Beitzah 12a): once permission to do these things was granted for food, it was also granted for other purposes. A yahrtzeit candle may not be lit on yom tov (because its light isn’t used. If one forgot to do so before yom tov, he should light it where they’re eating so that they’re actually using the light – Bi’ur Halacha 514:5 s.v. ner shel batalah).
98:2 Things we may not do on yom tov include making cheese, churning butter, and curdling milk with rennet or other things that have that effect on milk. Likewise, we may not separate the cream from the milk unless we leave a little on the milk below as we do on Shabbos. Even so, one may only do this for what he needs that day; he may not do so for the next day as that constitutes preparing on yom tov, which is prohibited. If one is in danger of a financial loss, he may have a non-Jew separate it for him in this manner.