How did the piece of wood turn the bitter water sweet?
Rashi (in Pesachim, 39a) and Ramban #1 (citing the Mechilta), Targum Yonasan and Midrash Tanchuma: The wood, like the water, was bitter, 1 and the fact that it turned the water sweet was a miracle within a miracle. 2
Ramban #2: Hashem taught Moshe that particular species of wood had in its nature to sweeten bitter water. 3
Targum Yonasan: Moshe wrote the Great Name of Hashem (Havayah) on it.
Rashi and Targum Yonasan: It was from a tre called 'Hirduf'.
Ramban Similar to that of Melachim 2, 2:21. And the Torah writes "Vayorehu" because Hashem showed Moshe where the wood was to be found, or because He brought it to him miraculously.
Ramban: Hence the word "Vayorehu" ('and He taught him').
What is the significance of the word "Vayorehu Hashem Eitz". What did Hashem teach Moshe?"
Ramban #3 (citing the Tanchuma): Hashem taught Moshe His ways - that He sweetens the bitter with things that are bitter.
What are "Chok" and "Mishpat" referring to?
Rashi and Ramban #1 (citing Sanhedrin 56b): They refer to Shabbos, Parah Adumah 1 and Dinim 2 (Mishpatim - civil laws), respectively.
Ramban #2: "Chok" and "Mishpat" 3 both refer to the customs and regular practices that Hashem introduced when they entered the great and awesome desert, customs to busy themselves with until they entered an inhabited land.
Ramban #3: With reference to "ve'Sham Nisahu", Hashem chastised them by making them suffer Chok - the law of the desert, to suffer hunger and thirst, thereby inducing them to cry out to Him (not by complaining), and Mishpat - He taught them a series of civil laws by which to live by - to learn to love one another, to obey the instructions of their leaders, laws of Tzeni'us regarding their wives and children; how to behave with respect towards peddlers who entered the camp to sell their wares, and how to behave ethically when plundering their enemies - not to indulge in the abominations of the other nations. 4
Da'as Zekenim: They refer to Kivud Av va'Eim, which is both a Chok and a Mishpat.
Targum Yonasan: They refer to Shabbos, Kibud Av va'Eim, Parah Adumah, and the Dinim of wounds and of K'nasos (fines). 5
Sanhedrin, 56b: They refer to Shabbos, Kibud Av va'Eim and Dinim. 6
Rashi in Va'eschanan Devarim, 5:16 includes Kibud va'Eim. See Sifsei Chachamim. See also answer #6 and note.
See Targum Yonasan, who lists the areas of Dinim that Hashem taught them.
The Ramban cites many cases where that is what "Chok" and "Mishpat" means (See for example Yirmeyah, 33:25 regarding "Chok", and Bereishis 40:13 regarding "Mishpat", and Yehoshua, 24:25 [Ramban]. See also Ba'al ha'Turim).
Ramban: See Devarim 23:10. See also Ramban DH 've'Chein bi'Yehoshua'.
See Peirush Yonasan.
See Torah Temimah, note 36, who elaborates.
What test is the Pasuk referring to?
Rashi and Rashbam: Hashem tested them by depriving them of water and watching their reaction. They failed by grumbling, instead of asking Moshe nicely to Daven on their behalf. 1
Ramban #1 (interpreting Rashi's statement in DH 'Sham Sam lo'): He introduced them to the aforementioned Mitzvos (in advance of Matan Torah) 2 to see whether they would accept them willingly and with joy, or reluctantly. 3
Ramban #2: Refer to 15:25:3:3.
Seforno: He tested Yisrael to see whether they would receive the Chok and Mishpat that He gave them at Marah, or whether they would reject them and revert to their old ways, because, provided that they would accept them and continue to observe them, they would not suffer the plagues of the Egyptians. 4
Targum Yonasan: Yisrael tried Hashem with ten tests. 5
See Ramban's objection to this explanation.
Just as Avraham Avinu performed the Mitzvos before they were commanded. It also trained them in the performance of Mitzvos (Ramban).
And the following Pasuk informed them that there were more Mitzvos to come (Ramban).
As the following Pasuk spells out (Seforno).
See Bartenura, Avos 5:4, and Na'ar Yonasan.
QUESTIONS ON RASHI
Rashi writes that Yisrael were commanded on Shabbos. But later, in 16:22, he writes that they were surprised to find double Manna on Friday, since they had not yet been told about Shabbos?
Moshav Zekenim: That is a D'rashah, and we do not challenge a Drashah. 1
Riva (16:1): Hashem told Moshe to tell Yisrael about Shabbos at Marah, but Moshe delayed telling them, like he delayed 2 telling them that extra Manna would fall on Erev Shabbos 3
Seemingly, the two D'rashos contradict each other. How can we resolve this D'rashah with the Pesukim below, that the Nesi'im told Moshe that they collected double? Perhaps they expected that they will receive a single portion, and miraculously, it will suffice for two days (like the dough that they took from Mitzrayim - refer to 16:1:1:1), or it will be blessed in the innards, and half the usual amount will suffice for each day (like the Seforno (Vayikra 25:19) says about the fruit of Erev Shemitah), or that extra manna will fall Friday afternoon, or that it will fall on Shabbos and they will eat it outside. Why did Moshe need to tell them to bake it today? Perhaps they thought that they must eat it raw on Shabbos, and if they change its form, it will spoil. (PF)
Riva said that to explain how they could travel to Midbar Sin on Shabbos, and transgress Techumim. How can the Riva learn from the Manna? There, Moshe intended to command them shortly before Shabbos, so no one would transgress. Here, why did he not tell them before Shabbos? And why did Moshe himself travel? (PF)
Rashi writes that they were commanded on Parah Adumah. What is the source for this? Sanhedrin 56b lists ten Mitzvos that they were commanded, and Parah Adumah is not among them?
Moshav Zekenim (citing Bechor Shor): Moshe asked how bitter wood can sweeten water 1 , and Hashem said that there is a Mitzvah like this - Parah Adumah, which is Metamei Tehorim (and Metaher Temei'im).
T'rumas Hadeshen (cited in Chumash Otzar ha'Rishonim): (The Torah writes "Chok u'Mishpat" and) Parah Adumah is called Chukas ha'Torah. 2
Moshav Zekenim (in Bamidbar 19:2): "Asher Tzivah Hashem" (Ibid.) implies that they were commanded previously, 3 and the Gemara in Sanhedrin 56b learns from there that they were commanded about Kivud Av va'Eim at Marah.
T'rumas ha'Deshen: Since Yisrael saw this miracle, they will be able to accept that the Parah Adumah is Metamei Tehorim and vice-versa. Otherwise, there was no need to teach it to them here.
Moshav Zekenim (Bamidbar, 19:2): This is not a proper answer. Many Mitzvos are called Chok , for example "Veshamarta es ha'Chukah ha'Zos" (Sh'mos 13:10)!
Moshav Zekenim: Even though the Torah writes "Zeh ha'Davar asher Tzivah Hashem" by Nedarim (30:2) and Shechutei Chutz (in Vayikra, 17:2), there Moshe tells Yisrael that this is what Hashem commands now. Here, [it says so before it mentions speaking to Yisrael - PF] it is what Hashem already commanded.
