Shevi'is Chapter 8, Mishnah 8. Our Mishnah continues the discussion of which uses of seventh year produce are permitted and which are forbidden on account of their sanctity. As we know, the verse says "l'ochlah" - for eating, and therefore anything that does not fall under the category of eating is not permitted with seventh year produce.
Purchases that may not be made with seventh year money:
"Ein lokchin avadim u'keraka'os u'behemah temei'ah midmei shevi'is" - one may not buy these three things with seventh year produce or with the money received for it:
Slaves.
Land.
A non-kosher animal - an animal that is not fit to be eaten.
"V'im lakach - yochal k'negdan" - if someone transgressed and bought one of these, he must take other food and eat it with the sanctity of the seventh year, as a replacement for the seventh year money that he used improperly.
Offerings that may not be brought with seventh year money:
The Mishnah continues: "Ein mevi'in kinei zavim v'kinei zavos v'kinei yoldos midmei shevi'is":
Kinei zavim - a zav is one of those people whom halachah obligates to bring a bird offering in order to be able to eat sacred foods.
Kinei zavos - the bird offering of a zavah.
Kinei yoldos - the bird offerings of women who have given birth.
None of these offerings may be brought with seventh year money, "v'im heivi - yochal k'negdan": someone who used seventh year money to bring these offerings must take other food and eat it with the sanctity of the seventh year as a replacement.
Why did the Mishnah single out precisely these offerings?
After all, seventh year money may not be used for any of the other offerings either. The commentators explain that the Mishnah chose these in order to teach us something new: since these offerings are what permit a person to eat sacred foods, and in a certain sense they exist for the sake of eating - not directly, but indirectly - one might have thought that they may be brought with seventh year money, for they open up access to certain kinds of food. The Mishnah therefore teaches that even for offerings of this kind, seventh year money may not be used.
Rubbing oil of the seventh year on utensils:
"Ein sachin kelim b'shemen shel shevi'is" - it was common practice to rub oil into certain utensils and certain types of vessels, and this may not be done with oil of the seventh year, since rubbing oil into utensils is not a use permitted under the sanctity of the seventh year. "V'im sach - yochal k'negdo": someone who transgressed and did so must eat food with the sanctity of the seventh year as a replacement for the oil he used.
In summary: in this Mishnah we learned of three uses that are forbidden under the sanctity of the seventh year - buying slaves, land or a non-kosher animal with seventh year money; bringing the bird offerings of a zav, a zavah or a woman who has given birth with seventh year money, even though these offerings permit the eating of sacred foods; and rubbing oil of the seventh year on utensils. In all of these cases, one who transgressed and did so must eat k'negdan, that is, he must eat other food with the sanctity of the seventh year as a replacement for what he spent improperly.