QUESTION: Rebbi Eliezer and Rebbi Yehoshua argue where the rains come from.
Rebbi Eliezer says that the rains come from clouds that absorb the water
from the sea. Rebbi Yehoshua says that the clouds fill up with water from
the waters above the sky (the "Mayim Elyonim"), and then the clouds drop
that water onto the earth. Rebbi Yehoshua challenges the opinion of Rebbi
Eliezer and asks that if the rains originate from the sea, then rain water
should be salty. Yet we know that it is not salty!
RASHI explains that we know that rain water is not salty because no grain
can grow from salty water. Why did Rashi choose this strange way to prove
that rain water is not salty? Rain water is collected in water pits from
which people drink, we know exactly how it tastes! Why does Rashi say that
the reason we know that rain water is not salty is because plants could not
grow from salty water? (REBBI AKIVA EIGER in GILYON HA'SHAS; see also the
commentaries printed in the EIN YAKOV, BEN YEHOYADA)
ANSWER: The motive behind Rashi's explanation could be as follows. The
Gemara cites a proof for the opinion of Rebbi Eliezer, who says that rain
water comes from the sea, from the verse, "A mist arose from the land and
watered all of the ground" (Bereishis 2:6). Rebbi Yehoshua, who says that
rain water comes from the upper waters, must respond to this proof. Rebbi
Yehoshua answers that the verse does not mean that the clouds collect their
waters from the earth itself, but rather that the clouds must rise up from
where they are to the upper heavens in order to receive the water from
there.
Why did Rebbi Yehoshua give that answer? There is a much simpler answer that
he should have given. He should have said that the verse is not describing
the physical nature of rain, as Rebbi Eliezer understands it, but rather the
verse is discussing a singular event that occurred only once in the history
of the world -- at the time of Creation, the water that fell onto the ground
came from the sea. Normal rain, though, comes from the waters above, as is
evidenced by the fact that the water is not salty. (The ETZ YOSEF in the Ein
Yakov is bothered by this question.)
It must be that Rebbi Yehoshua somehow knew that even the rain that fell at
the time of Creation could not have come from the sea, and that is why he
did not give this answer. How, though, did Rebbi Yehoshua know this? The
Torah does not tell us anything about the taste of that water! Therefore,
Rashi understood that since the verse says that the water that fell at
Creation watered the ground and caused all of the plants to sprout forth, it
must be that the rain that fell was not salty, because plants cannot grow on
salt water. That is why Rashi proves that rain water is not salty from the
fact that *plants cannot grow* with saltwater! (M. Kornfeld)