1) THE GIFTS GIVEN IN THE MERIT OF MOSHE RABEINU, AHARON, AND MIRIAM
QUESTION: The Gemara says that the well, cloud, and Man were gifts to the Jewish people in the merit of Miriam, Aharon, and Moshe Rabeinu respectively.
The Gemara here seems to contradict the Gemara in Bava Metzia (86b). The Gemara there cites Tana d'Vei Rebbi Yishmael who states that in the merit of the three acts which Avraham Avinu performed when he served his guests, the Jewish people merited to receive three gifts when they sojourned in the wilderness: the Man, the cloud that protected them, and the well of Miriam.
The Gemara there does not mention that these three things were in the merit of Miriam, Aharon, and Moshe Rabeinu. Moreover, the Gemara there explicitly refers to the well as "Be'erah Shel Miriam," the well of Miriam, which clearly implies that the well was in the merit of Miriam. Why, then, does the Gemara there say that the well was in the merit of Avraham Avinu? (MAHARSHA to Bava Metzia 86b)
(a) The MAHARSHA answers that in the merit of Avraham Avinu's three deeds with his guests, the Jewish people would have received only a momentary miracle of the Man, cloud, and well. It was in the merit of Moshe, Aharon, and Miriam that these miracles continued for many years while the Jewish people sojourned in the wilderness. This is why the cloud departed when Aharon died, the well disappeared when Miriam died, and the Man stopped falling when Moshe Rabeinu died.
(b) The BEN YEHOYADA writes that Hash-m originally designated these three gifts -- the Man, the cloud, and the well -- to be given to the Jewish people in the merit of Avraham Avinu's deeds. However, when the time came for the Jewish people to leave Mitzrayim and receive the gift of the cloud, they did not deserve that gift. The verse relates that they left Mitzrayim "b'Yad Ramah" (Shemos 14:8), which can be translated as "with a haughty spirit" (this translation is in clear contrast to the normal understanding of those words). As a result of their haughtiness, they lost the merit to receive the protection of the cloud. Hash-m gave them the cloud only in the merit of Aharon.
When the Jewish people consumed all of the food which they had brought with them when they left Mitzrayim, they should have received the gift of the Man in the merit of Avraham Avinu. However, they lost that merit when they complained, "You took us out into this wilderness to kill us with starvation!" (Shemos 16:3). Hence, it was given to them only in the merit of Moshe Rabeinu.
Similarly, when the people arrived at Refidim, they should have received the gift of the well in the merit of Avraham Avinu. However, the people sinned there when they complained to Moshe Rabeinu, and they lost the merit to receive the gift of the well. However, Hash-m gave them the gift of the well in the merit of Miriam.
(c) RAV CHAIM SHMUELEVITZ zt'l in SICHOS MUSAR (5732, #8) gives a metaphor to answer this question. Although a small seed is able to sprout into a huge tree, the seed itself cannot sprout without external factors contributing to its growth, such as soil, water, and sunshine.
Rav Chaim Shmuelevitz explains that when the Gemara in Bava Metzia says that the gifts of the Man, cloud, and well were granted in the merit of Avraham Avinu, it means that the "seeds" of these gifts -- the initial reason for granting them -- were given in the merit of the Chesed of Avraham. However, these "seeds" needed additional factors to cause them to sprout and come to fruition -- these were the merits of Moshe, Aharon, and Miriam. (I. Alsheich) (See also Insights to Bava Metzia 86:3.)
2) THE PROOF THAT RAINWATER IS NOT SALTY
QUESTION: Rebbi Eliezer and Rebbi Yehoshua argue about the source of rain. Rebbi Eliezer says that rain comes from clouds which absorb the water from the sea. Rebbi Yehoshua says that the clouds fill up with water from 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 rainwater should be salty, but rainwater is not salty.
RASHI explains that the proof that rainwater is not salty is because no grain can grow from salty water.
Why does Rashi choose to give this strange way of proving that rainwater is not salty? It is obvious that rainwater is not salty because people drink rainwater and nobody finds that it tastes salty. Why does Rashi say that the proof that rainwater is not salty is because plants cannot grow from salty water? (REBBI AKIVA EIGER in GILYON HA'SHAS; see also EIN YAKOV and BEN YEHOYADA.)
ANSWER: Rashi's explanation may be motivated by the following consideration. The Gemara cites proof for the opinion of Rebbi Eliezer from the verse, "A mist arose from the land and watered all of the ground" (Bereishis 2:6), which clearly implies that rainwater originates from the earth. Rebbi Yehoshua, who says that rainwater comes from the upper waters, responds 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 the earth to the upper heavens in order to receive the water from there.
There is a much simpler answer that Rebbi Yehoshua should have given. He should have said that the verse does not describe the physical nature of rain, as Rebbi Eliezer understands it, but rather the verse discusses 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, in contrast, comes from the waters above, as is evidenced by the fact that the water is not salty. (The ETZ YOSEF in the Ein Yakov discusses this question.)
Apparently, Rebbi Yehoshua had reason to be certain that even the rain that fell at the time of Creation could not have come from the sea, and that is why he gave another answer, an answer which would explain how even the rain at the time of Creation did not come from the sea. How, though, did Rebbi Yehoshua know that the rain at the time of Creation did not come from the sea? Perhaps that water indeed came from the sea (and indeed was salty).
It is for this reason that Rashi writes that Rebbi Yehoshua's argument was that salty water cannot grow crops. Since the verse says that the water that fell at Creation watered the ground and caused all of the plants to sprout, that rain must not have been salty because plants cannot grow from salty water. That is why Rebbi Yehoshua insists that even the misty rain of Creation did not originate in the sea. (M. Kornfeld)