Menahot, Chapter Eleven, Mishnah Three
This mishnah discusses the griddle cakes offered daily by the High Priest (Leviticus 6:13-15).
1) The high priests griddle cakes: their kneading, their shaping, and their baking were performed within [the Temple Court],
2) And they override the Shabbat.
3) The grinding [of the grain for it] and the sifting did not override the Shabbat.
4) Rabbi Akiva said a general rule: any work that can be done on the eve of Shabbat does not override Shabbat, but that which cannot be done on the eve of Shabbat does override Shabbat.
Section one: When it comes to the high priests griddle cakes, all agree that they must be prepared and baked in the Temple. The reason is that these griddle cakes are anointed with oil in the Temple. This makes them holy and they cannot subsequently be taken out to be kneaded, shaped or baked outside the Temple.
Section two: These cakes were offered every day. Therefore, these three actions, which are performed on the same day that they are offered, can be performed on the Shabbat. As Rabbi Akiva says in section four, any action that cannot be performed the day before, overrides the Shabbat.
Section three: However, grinding grain to make these cakes and sifting the grain to make the flour are not essential parts of the minhah offering. Rather they are preparatory acts, and therefore they can be performed on Friday. As Rabbi Akiva states, anything that can be done before Shabbat, does not override Shabbat.
Section four: This is the general rule that governs when something overrides the Shabbat.