שולחן ערוך אורח חיים · סימן תק״ג

English

Not to prepare on one Yom Tov for the next. 2 sections: It is forbidden to bake, cook, or slaughter on Yom Tov for the needs of the next day — even if it is Shabbat or Yom Tov, and even for the two days of Rosh Hashanah. However, a woman may fill a pot with meat even though she only needs one piece. Rema: All the more so one may slaughter even though one only needs a small amount. (Semak) Similarly one may cook many pots and eat a little from each one. [Beit Yosef, Rabbeinu Yerucham, and responsum of Rashba] This applies specifically before eating, but after eating she may not cook and claim she will eat a little from it, as that would be a ruse. However if she transgressed and cooked [or slaughtered], it is permitted to eat it.

English

A baker may fill an entire barrel of water even though he only needs one jug. Rema: But he must place everything near the fire at once — it is forbidden to add more once the barrel is already near the fire, as that is unnecessary extra effort. (HaMagid ch. 1)