Parah, Chapter 11, Mishnah 9. This is the closing mishnah of the chapter, and it turns to the instrument through which the whole purification is carried out: the eizov, the hyssop, which is dipped into the mei chatas and used to sprinkle upon the person or vessel that has contracted tumah. Here the Mishnah tells us what kind of hyssop qualifies for the mitzvah, and what still works after the fact.
The Mishnah opens by fixing the minimum form of the plant. "Mitzvas eizov shloshah kolchim": to perform the mitzvah one needs a hyssop with three kolchim, three woody twigs. "Uveihem shloshah giv'olin": those twigs must carry three giv'olin between them. On the first view the arithmetic is straightforward, one stalk to each twig, so that three twigs yield three stalks in all. Picture a small woody branchlet with a single flowering stem rising out of its top. The lower woody piece is what the Mishnah calls a koleich, and the stem that emerges from it is the giv'ol. Gather three such branchlets, each topped by its one stem, and you have an eizov that meets the requirement.
"Rabbi Yehudah omer: sheloshah sheloshah." Rabbi Yehudah raises the requirement considerably. In his view every one of the three shoots must itself bear three separate stalks, so that the branch is not counted by a single bloom but by a set of three.
The Mishnah now describes how the plant is handled. "Eizov sheyeish bo shloshah kolchim": when one has before him a hyssop that bears the three required twigs, "mefasko ve'ogdo", he pulls the twigs apart from one another and afterwards ties them into a single bundle. That two-stage handling, first the separating and then the binding, is the ideal performance of the mitzvah.
But what if the preparation was incomplete? "Pisko velo agado", he separated the shoots but never bound them; "agado velo pisko", he bound them but never separated them; "lo pisko velo agado", he did neither one. In all of these cases the Mishnah rules "kasher": bedi'eved, after the fact, the eizov may still be used.
The chapter closes with the view of Rabbi Yose. He states the baseline in the same terms, "mitzvas eizov shloshah kolchim, uveihem shloshah giv'olin": three twigs bearing three stalks. To this he attaches a concession. "Ushe'yarav shenayim": should the plant be reduced until only two of its stalks survive intact, "vegardumav kolshehu", while the third has been worn down to no more than a remaining stub, the eizov has not lost its fitness and may be used.
Where do these two requirements, that there be three and that they be bound, come from? They are derived by a gezeirah shavah built on the word of taking, "lekichah", which appears here and also appears in connection with Pesach, where the Torah speaks of taking a bundle of eizov to apply the blood. By Pesach the bundle means three shoots, since a bundle is never fewer than three, and by Pesach the shoots are bound together into an agudah. So here too: three shoots, and bound together.
A practical detail on the severing. If the shoots were cut but not cut all the way through, so that they are still held to one another by the skin of the plant, this is the very case that the Mishnah calls "agado velo pisko", bound but not separated. So writes Tosafos Rabbi Akiva Eiger.
And what is the measure of the "gardum", the stump that Rabbi Yose allows? The Rambam gives it a size: the remnant must be at least a tefach, a handbreadth, in order to be counted at all.
Finally, note the relationship between the two views on this point. Rabbi Yose requires that two full stalks remain and permits only one of them to be reduced to a stump. The first opinion in the Mishnah is more lenient still, holding that even one remaining stalk together with two stumps leaves the eizov fit for the sprinkling.