We have already established that, based on the passage in Sh’mot 12:16, food preparation is permitted on Yom Tov. The Mishna on our daf discusses the preparation of spices and salt. We find that Beit Shammai insist that some change be made in the way spices are ground up (grinding is one of the activities ordinarily forbidden on Shabbat), while Beit Hillel allow grinding to be done normally. Both agree, however, that salt should be ground in an out-of-the-ordinary way – by using a wooden pestle rather than the standard stone pestle.
What is the reason for this? Rav Huna and Rav Hisda disputed this issue. One of them said: Everyone knows that all dishes require salt, and therefore one should prepare salt the day before the Festival. Since he failed to do so, this task may be performed on the Festival only in an unusual manner. But not all dishes require spices, and therefore it is possible that on the day prior to the Festival, one was not aware that he would require spices on the Festival.
And the other one said a different reason: All spices lose their flavor and cannot be prepared ahead of time, and salt does not lose its flavor, which means one could have prepared it the day before. Since he neglected to do so, he may prepare salt on the Festival only in an unusual manner.
The discussion that takes place in the rishonim revolves around the question of how we are to regard salt: Is salt considered a food, or is it merely an ingredient that is used in preparing food – makhshi’rei okhel nefesh? If it is the latter, then we can well understand that it cannot be prepared in the normal way, since makhshi’rei okhel nefesh are not included in the things that are permitted based on Sh’mot 12:16. If, however, salt is considered food, then why should we not permit it to be prepared as it always is?
The Ran and Re’ah suggest that salt is different than other foods because it is not usually ground at home in small quantities. Ordinarily salt is prepared commercially and ground up in large amounts, and such preparation appears to be a weekday activity – a ma’aseh hol – which is why a change in the method of preparation is required.