THESE ARE THE COMMODITIES WITH WHICH A MAN DISCHARGES HIS OBLIGATION ON PASSOVER: WITH WHEAT, WITH BARLEY, WITH SPELT, WITH RYE, AND WITH OATS
The text refers to “discharging his obligation” because the Passover commandment is not only to refrain from eating leaven, but also the responsibility to eat matzah – at least on the first night. (see Ex. 12:18)
These five listed grains are also the ones which are forbidden during Passover if they have not been prepared as matzah. However, the exact grains are somewhat unclear. The Talmud continues by giving Aramaic names to the species. Other grains like rice and corn are discussed
R. Johanan b. Nuri prohibits [the use of] rice and millet, because it is near to turn leaven. The scholars asked: does ‘because it is near to turn leaven’ mean that it quickly becomes leaven, or perhaps it is near to leaven, but is not completely leaven? — Come and hear: For it was taught, R. Johanan b. Nuri said: Rice is a species of corn and kareth (Divine punishment) is incurred for [eating it in] its leavened state, and a man discharges his obligation with it on Passover.
A fun story is told about the rabbis discussing a particular pastry made with dough kneaded with wine, oil or honey. Is eating it subject to kareth or not?
Now, R. Papa and R. Huna son of R. Joshua sat before R. Idi b. Abin, while R. Idi b. Abin was sitting and dozing. Said R. Huna son of R. Joshua to R. Papa: What is Resh Lakish's reason? — He replied, Scripture saith, Thou shalt eat no leavened bread with it etc.: [In the case of] the commodities with which a man discharges his obligation in respect of unleavened bread, kareth is incurred for [eating them in] their leavened state; but [with regard to] this [dough], since a man cannot discharge his obligation therewith, because it is “rich matzah”, kareth is not incurred for its leaven.
Matzah is supposed to be the “bread of poverty” – not a rich treat! The argument continues for some time, when suddenly:
R. Idi b. Abin awoke [and] said to them, Children! This is the reason of Resh Lakish, because they are fruit juice, and fruit juice does not cause fermentation.
Wake up and smell the fruit juice!