Parah 11:9-12:1

Parah 11:9

The mitzvah of hyssop requires three shoots with three stalks; Rabbi Yehuda says that each shoot must have three stalks. A hyssop of three shoots should be separated and then tied together. If the shoots were separated but not tied together, or tied together but not separated, or neither separated nor tied together, they are still valid. Rabbi Yosi says that the mitzvah of hyssop is three shoots with three stalks but its remnants (if one shoot is lost) only need two stalks and its stumps (if the shoots break) may be of any size, however small.

Parah 12:1

Short hyssop may be extended using thread or a spindle reed. One dips it into the sanctification water and raises it up. He then holds it by the actual hyssop (rather than its extension) and sprinkles with it. Rabbi Yehuda and Rabbi Shimon say that just like the sprinkling must be done with the actual hyssop, the dipping must also be done with the actual hyssop.