Oktzim, Chapter Three, Mishnah Six
1) Unripe figs or grapes:
a) Rabbi Akiva says: they convey food uncleanness;
b) Rabbi Yohanan ben Nuri says: [this is only] when they have reached the season when they are liable to tithes.
2) Olives and grapes that have hardened:
a) Bet Shammai says: they are susceptible to uncleanness,
b) Bet Hillel says: they are insusceptible.
3) Black cumin:
a) Bet Shammai says: is not susceptible,
b) Bet Hillel says: it is susceptible.
4) Similarly [they dispute with regard to their liability to] tithes.
Section one: According to Rabbi Akiva, although they are not yet ready to eat, unripe grapes and figs are already considered food and therefore they convey food uncleanness. Rabbi Yohanan ben Nuri says that this is so only when they become liable to tithes. Their liability to tithes is discussed in Sheviit 4:7-8.
Section two: The mishnah now moves to the opposite scenarioolives and grapes that have hardened. Bet Shammai says that they are nevertheless still considered food. Bet Hillel says that since they are generally no longer eaten, they are no longer considered food.
Section three: Bet Shammai says that black cumin which is not eaten but just put on the top of bread is not considered food and therefore is not susceptible to impurity.
Bet Hillel says that since it is eaten, it is considered food.
Section four: The same dispute occurs with regard to tithing black cumin. Bet Shammai says it is not food and therefore need not be tithed. Bet Hillel says it is liable for tithes because it is food.