Parah, Chapter 3, Mishnah 5. This chapter describes the preparation of the Kohein who was to burn the parah adumah. During the seven days of his separation, he was sprinkled with waters mixed from the ashes of the parah adumahs that had been prepared in earlier generations. Our mishnah addresses a practical question: what if the ashes of all seven earlier cows were not available? And then it turns to a fascinating historical accounting: who, over the course of Jewish history, actually prepared these cows?
The opening clause is "Lo matzu misheva": if ashes from seven earlier cows could not be located. The ruling then descends step by step. "Osin misheish" - the sprinkling was done with ashes from six. Failing six, "meichameish", with five; "me'arba", with four; "mishalosh", with three; "mishtayim", with two; and at the end of the line, "umi'achas", with the ashes of one single cow. The preference, then, was to draw upon as many of the previous cows as could still be had, yet the avodah was never suspended for want of them. Where nothing survived but the ashes of a lone parah, the Kohein received his sprinkling from those ashes throughout the week he was kept apart, and that sprinkling accomplished everything it needed to, leaving him qualified to burn the new cow.
Who prepared them?
A fresh question is now posed: "Umi asan?" By whose hand were these cows prepared? Rebbi Meir answers by counting them off. "Harishona asa Moshe": the very first was the work of Moshe Rabbeinu. "Vashniya asa Ezra": the one after it belonged to Ezra. "Vachameish me'Ezra va'eilach": an additional five were made in the generations that came after Ezra's time. Such is the reckoning of Rebbi Meir.
"Vachachamim omrim: sheva me'Ezra va'eilach." The Chachamim disagree with the tally and hold that seven cows were prepared from the time of Ezra and on, beyond the earlier ones.
The mishnah proceeds to record by name the Kohanim of that later era. "Shimon Hatzaddik veYochanan Kohein Gadol" - concerning these two it says "asu shtayim shtayim", that each one of them prepared a pair of cows. Three more are then listed, each credited with a single parah: "Elyo'einai ben Hakof", "veChanamel Hamitzri", and "veYishmael ben Piabi", of whom the mishnah states "asu achas achas". Together this is the roster of cows prepared across the span reaching from Ezra's generation down to the churban of the Beis Hamikdash.
Why would Shimon Hatzaddik and Yochanan Kohein Gadol each have prepared two cows rather than one? One approach is that the first cow of each of them was subject to a disqualification, so that a second had to be prepared in its place. The Chachamim, however, held that all of these cows were entirely fit, and each was counted in its own right.
Our mishnah leaves us with two thoughts side by side. On the one hand, the service of the parah adumah was never allowed to become impossible: even the ashes of a single cow sufficed to prepare the Kohein for the next one. On the other hand, over the many centuries of the Beis Hamikdash, so few parah adumahs were ever prepared that the mishnah can list every one of them, and every Kohein who prepared them, by name.