ירמיהו לא:כט מקורות במשנה: Mishnah Oktzin

Unripe figs or grapes: Rabbi Akiva says: they convey food uncleanness; Rabbi Yohanan ben Nuri says: [this is only] when they have reached the season when they are liable to tithes. Olives and grapes that have hardened: Bet Shammai says: they are susceptible to uncleanness, Bet Hillel says: they are insusceptible. Black cumin: Bet Shammai says: is not susceptible, Bet Hillel says: it is susceptible. Similarly [they dispute with regard to their liability to] tithes.