Mishnah Parah 11:9: The mitzvah of the hyssop [which the Torah commanded to be used for sprinkling the chatat waters on one who is impure] is three stems [bundled together] containing three [central] stalks [i.e. a stalk for each]. Rabbi Yehuda says: three [stalks] each. A hyssop that has three stems, one separates them and then binds them together. If one separated but did not bind, [or] bound and but did not separate, [or] neither bound nor separated, it is valid [for sprinkling, post-facto]. Rabbi Yose says: The mitzvah of the hyssop is three stems containing three [central] stalks, and two for its remainder [i.e. if some of it falls off, it must retain at least two stalks in order to stay valid], and a [minimal] amount for its frame [i.e. if the sprinkling causes the stalks to break, at least a minimal amount must remain in order for to stay valid].

מִצְוַת אֵזוֹב, שְׁלשָׁה קְלָחִים וּבָהֶם שְׁלשָׁה גִבְעוֹלִין. רַבִּי יְהוּדָה אוֹמֵר, שֶׁל שְׁלשָׁה שְׁלשָׁה. אֵזוֹב שֶׁיֶּשׁ בּוֹ שְׁלשָׁה קְלָחִים, מְפַסְּגוֹ וְאוֹגְדוֹ. פִּסְּגוֹ וְלֹא אֲגָדוֹ, אֲגָדוֹ וְלֹא פִסְּגוֹ, לֹא פִסְּגוֹ וְלֹא אֲגָדוֹ, כָּשֵׁר. רַבִּי יוֹסֵי אוֹמֵר, מִצְוַת אֵזוֹב, שְׁלשָׁה קְלָחִים, וּבָהֶם שְׁלשָׁה גִבְעוֹלִים, וּשְׁיָרָיו שְׁנַיִם, וְגַרְדֻּמָּיו כָּל שֶׁהוּא:

Mishnah Parah 12:1: The short hyssop [which is not long enough to reach the bottom of the vessel containing the chatat waters], one should provide it with string or a rod and dip it, and raise it [out], and hold the hyssop and sprinkle with it. Rabbi Yehuda and Rabbi Shimon say: Just as sprinkling must be [done] with the hyssop, so too dipping must be [done] with the hyssop.

הָאֵזוֹב הַקָּצָר, מְסַפְּקוֹ בְחוּט וּבְכוּשׁ, וְטוֹבֵל וּמַעֲלֶה, וְאוֹחֵז בָּאֵזוֹב וּמַזֶּה. רַבִּי יְהוּדָה וְרַבִּי שִׁמְעוֹן אוֹמְרִים, כְּשֵׁם שֶׁהַזָּיָה בָאֵזוֹב, כָּךְ טְבִילָה בָאֵזוֹב: