Parah, Chapter 11, Mishnah 3. Our chapter deals with mei chatas, the water into which the ashes of the parah adumah have already been mixed, and with the delicate two-way relationship between that water and whatever comes into contact with it. Mei chatas has the power to render a person tamei, and it can itself be rendered unfit. This mishnah presents an unusual case that puts both sides of that relationship on display: a piece of terumah food that tumbles into the water, is fished out, and eaten.
The Text
The subject of the first clause is a fig cake: "Dveilah shel terumah," a pressed round of figs carrying the status of terumah. Its mishap is described next: "shenafal letoch mei chatas," it tumbled into the chatas water. And then, "unetalah va'achalah," someone drew it out of the water and consumed it.
From here the mishnah divides the case by measure. "Im yesh bah kabeitzah": should the cake amount to the volume of an egg, then "bein temeiah bein tehorah," whatever its status happened to be before it fell in, tamei or tahor, the outcome is identical: "hamayim temei'in," the water contracts tumah, "veha'ochlah chayav misah," and the one who ate the cake is chayav misah.
The opposite measure yields a split verdict. "Ein bah kabeitzah": where the cake falls short of an egg's volume, "hamayim tehorin," the water is unaffected and stays tahor, and yet "veha'ochlah chayav misah," the eater is nonetheless chayav misah. All of this is taught by the Tanna Kamma.
An objection follows. "Rabbi Yose omer: bitehorah, hamayim tehorim." Rabbi Yose holds that where the cake had been tahor at the moment it fell, the water suffers nothing and remains tahor.
A second, separate case rounds out the mishnah. "Hatahor lechatas": someone who has reached the elevated standard of taharah demanded of one who handles the parah adumah water (throughout these discussions we are speaking of kohanim), "shehechnis rosho verubo," who lowered his head together with the larger part of his frame, "letoch mei chatas," into the chatas water itself, "nitma," he contracts tumah.