Shevi'is, Chapter 5, Mishnah 4. This mishnah deals with produce that grew mainly during the sixth year, before Shemittah, so that all that remains to be done in the seventh year is to pull it out of the field. What is the proper way to do this?
The three cases in the mishnah:
"Luf shel erev shevi'is shenichnas lashevi'is" - a type of onion that is indeed in the ground during the seventh year, but does not grow during it; its growth is completed before then.
"Betzalim hakeitzim" - summer onions, which likewise complete their growth in the sixth year.
"Pu'ah shel iddis" - a plant used for dyeing things, which grows in 'iddis' - a field of superior quality.
What all three have in common: this is permitted produce, since its growth took place in the sixth year, and it merely remained in the ground into the seventh year.
The dispute between Beis Shammai and Beis Hillel about the manner of uprooting:
"Beis Shammai omrim: okrin osan b'ma'arufos shel etz" - with rakes made of wood, which is not the usual manner of uprooting. The reason: a change is required here, to do it in a manner different from the norm, so that a person will not appear to be working the land during Shemittah.
"U'Beis Hillel omrim: b'kardumos shel matachos" - one may use implements made of metal.
Two approaches have been offered in understanding the position of Beis Hillel:
Some understand that since metal is permitted, there is no requirement of a change at all, for using metal involves no departure from the usual practice.
Others understand that the very use of axes rather than hoes - that is, a type of spade - constitutes at least a minimal change; it is only that Beis Hillel do not require the maximal change.
"U'modim b'pu'ah shel tzela'os":
Beis Shammai also agree in the case of this pu'ah - the very same dye plant, except that it comes from the 'tzela'os'. Various explanations have been offered as to what this term refers to, but the common denominator among the understandings is that uprooting it from the ground is far more difficult. Therefore Beis Shammai too agree that it may be uprooted with metal axes.
In summary: in this mishnah we learned about produce that grew during the sixth year and remained in the ground into the seventh, and about the manner of uprooting it: Beis Shammai require a change from the usual manner of uprooting - wooden rakes - so that one will not appear to be working the land; Beis Hillel permit metal axes, and in understanding their view there are two approaches, whether no change is required at all or only a minimal change; and regarding pu'ah of the tzela'os, which is especially difficult to uproot, all agree that it may be uprooted with metal axes.