Why the Bitter Waters of Marah Were Sweetened by Torah

[(Exodus 15:22, continued:) "They went three days in the wilderness and found no water."] Rabbi Yehoshua says: When Israel crossed through the sea, sweet water came forth for them, and from it they took into their vessels and drank. But once the water was used up, they began to complain, as it is said, "And the people murmured against Moses, etc." (Exodus 15:24). "And they came to Marah" (Exodus 15:23). They ought to have taken counsel with the greatest one among them; instead they arose and complained. Rabbi Elazar of Modi'in says: Israel was accustomed to speaking words of complaint before the Holy One, blessed be He. Immediately, "And he cried out to the LORD, and the LORD taught him a tree" (Exodus 15:25). It does not say "and He showed him" (vayar'ehu), but rather "and He taught him" (vayorehu). Rabbi Shimon ben Yochai said: He taught him [something] from the Torah, concerning which it is written, "It is a tree of life" (Proverbs 3:18). The Holy One, blessed be He, taught him, and he spoke over the water, and it became sweet.