Orlah Chapter 3, Mishnah 7. In the previous Mishnah we learned about bundles of fenugreek of kilei hakerem, which according to Rabbi Meir are not nullified even in more than one part in two hundred. The basis for this ruling is found in the Mishnah before us.
The view of Rabbi Meir:
"She'hayah Rabbi Meir omer: es she'darko limanos mekadesh" - anything that is normally counted as an individual item, and is not customarily sold by weight or by volume but rather unit by unit, is shown by that very counting to be significant, and therefore it renders the mixture forbidden and is not nullified.
Why does the Mishnah use the term "mekadesh" (renders it consecrated)? Because with regard to kilei hakerem, in a mixture of this type, the verse states "pen tikdash ha'meleiah" - lest the whole crop become forbidden, its prohibition requiring that it be burned and destroyed. From here we see that Rabbi Meir holds that anything significant enough to be counted individually renders the mixture forbidden, and is not nullified even in one part in two hundred.
The view of the Sages and Rabbi Akiva:
The Sages disagree with Rabbi Meir and rule: "Ein hamekadesh ela shishah devarim bilvad" - this is not a blanket rule covering every item that is counted individually; rather, only six items are so significant in common use that they are not nullified. Rabbi Akiva adds a seventh item to them.
"V'eilu hem" - these are the six items listed by the Sages:
"Egozei perech" - a particular type of nut, which comes from a place called Perech.
"Rimonei badan" - pomegranates that come from a place called Badan.
"V'chaviyos stumos" - sealed barrels of wine.
"V'chalafos teradin" - the shoots of the beet plant.
"V'kalchei keruv" - cabbage stalks.
"U'dela'as Yevanis" - Greek gourd.
To these Rabbi Akiva adds a seventh item: "Af kikar shel ba'al habayis" - loaves of bread made by the woman of the house, baked privately at home.
In which laws is this rule stated:
All of these items render a mixture forbidden in two areas:
Orlah: in those items to which orlah can apply, meaning those that come from a fruit tree. Even though orlah is generally nullified in one part in two hundred, these items are not nullified.
Kilei hakerem: such as grain or another crop that grew in a vineyard, and the like. Kilei hakerem too is generally nullified in one part in two hundred, but these items are not nullified - because of their significance.
In summary: in this Mishnah Rabbi Meir and the Sages disagree about the scope of the rule that a significant item is not nullified. According to Rabbi Meir, anything that is normally counted renders a mixture forbidden and is not nullified; according to the Sages, only six items render a mixture forbidden, and Rabbi Akiva adds a seventh - a homeowner's loaf. This rule applies both to the laws of orlah and to the laws of kilei hakerem, both of which are nullified in one part in two hundred, except in the case of these significant items.