Why only beginning with the fourth plague is the exemption of the Jews mentioned?

Question

In Moshe's warning to Pharaoh (in Hashem's name) of the fourth plague, arov, he adds (Ex. 8:18-19):

וְהִפְלֵיתִי בַיּוֹם הַהוּא אֶת-אֶרֶץ גֹּשֶׁן אֲשֶׁר עַמִּי עֹמֵד עָלֶיהָ לְבִלְתִּי הֱיוֹת-שָׁם עָרֹב... וְשַׂמְתִּי פְדֻת בֵּין עַמִּי וּבֵין עַמֶּךָ

"I will distinguish at that time the land of Goshen, where My people are located, that there shall not be arov there... I will make a separation between My people and yours."

Similar statements are made concerning the plagues of pestilence (9:4) and the death of the firstborn (11:7). About the hail and the darkness, Moshe doesn't say anything to this effect, but the narrative records that the Jews weren't affected (9:26, 10:23). Nothing is said explicitly regarding any of the other plagues.

Why is this? According to the Midrash (Shemos Rabbah 9:10) that, for example, the plague of blood didn't affect the Jews either, why is this "distinction" spelled out only beginning with arov? Conversely, are there any sources that suggest that some of the plagues indeed did affect the Jews, and that they were exempted only from the ones where it's specified otherwise?

Answer 1

• The Ibn Ezra (7:24) says that Jews were affected by the first three plagues (Blood, Frogs, and Lice), since:

  1. That's the story the verses tell
  2. They weren't that bad (i.e. only an inconvenience, I guess. - he says that the Jews also dug for water)

  They were spared from Wild Animals because it was a harsh plague. They were also spared from Pestilence and Hail for the sake of their animals.

  They were not spared from Boils. The Ibn Ezra doesn't give a reason, but I guess it's because the verse doesn't mention it.

  They were not spared from Locusts, since they were leaving anyway and didn't need the crops.

• The Lubavitcher Rebbe (Likutei Sichot vol 11, pg 31-32) brings (and questions) the Radvaz who disagrees with the Ibn Ezra's interpretation and brings proofs from the verses.

  Then the Rebbe brings the Rambam (in his Commentary on the Mishna - Avot 5:4) who says that the Jews were not affected by Blood or Frogs, but were affected (albeit without pain) by Lice.

  The Rebbe then says that Rashi agreed that the simple meaning of the verses indicate that the Jews were affected by the first 3 plagues. The first two plagues were to attack the god of the Egyptians, the Nile River. If part of the River was unaffected, Pharaoh would use this as a proof that the Nile was stronger than G-d, which is why everyone was affected.

  The plague of Lice was intended to get the Egyptian magicians to admit that it was "the Finger of G-d". If the plague was limited in anyway, the magicians would say that all the plague proved was that Moshe and Aharon were better magicians than they were, since they couldn't produce the lice at all, but even Moshe and Aharon couldn't make the lice extend over the whole country of Egypt. Therefore even the Jews in Goshen were affected by the Lice.

  Only after that was the separation between the Jews and the Egyptians made (as the verses testify with regards to the Wild Animals).

  [I learned somewhere, but I can't find it now, that the fact that the Jews were not affected by the Wild Animals made the plague even more apparent that it was the work of G-d, since man made borders mean nothing to wild animals, yet they stayed out of the Jewish area]

As the Rebbe says in Chapter 10 of the Sicha, the simple meaning of the verses differs from the interpretation of the Midrash.

Answer 2

@Menachem's answer addresses your question regarding sources that suggest that some of the plagues affected the Jews as well as the Egyptians. However, regarding your question of why the distinction is "spelled out" only prior to the fourth plague, arov, I will offer the explanation of Abarbanel (who, by the way, believes that the Jews were not affected by any of the plagues):

According to Abarbanel, God intended to make three things known with the plagues: (1) that He exists, (2) that he controls worldly events, and (3) that there exist no other gods. The plagues were grouped (according to דצ"ך עד"ש באח"ב) with each group corresponding to one of the "themes" above. Thus, arov corresponds to a breaking point, the beginning of the plagues that were to show God's dominion over the world. Part of this was "וְהִפְלֵיתִי בַיּוֹם הַהוּא אֶת אֶרֶץ גֹּשֶׁן אֲשֶׁר עַמִּי עֹמֵד עָלֶיהָ"; that God had the power to inflict punishment on those who deserve it while sparing his people from harm. This is why Moshe introduces this plague with the information that it will not affect the Jews in Goshen, as well as concluding with "לְמַעַן תֵּדַע כִּי אֲנִי יְהוָה בְּקֶרֶב הָאָרֶץ".

Answer 3

The commentary of Rambam to Avos 5:4 reads (in my own, loose translation):

… and the wording of the Torah about every single plague among them [=the ten plagues] was that God brought [it] upon the Egyptians only, except the plague of lice, where it did not say so explicitly: rather, it's known that the Jews were not punished [with lice] but [the lice] were found near them, not bothering them. So explained the sages. (But for the other plagues the matter is clarified: at blood it says "the Egyptians could not drink water from the river", ….)

I propose that since, according to the Rambam (or the sages he cites), the Jewish area, Goshen, was affected by lice, the distinction between Goshen and the Egyptians areas was spelled out starting only with the next plague.

Answer 4

Ramban to Shemot 8:18 explains that the first three plagues were [more or less] static, and thus it is not surprising that their effects did not spill over into Goshen. It is only with the fourth plague, where one would have expected the wild animals to move into Goshen, that is is stressed that they remained outside.

He offers similar explanations regarding the fifth plague (Shemot 9:3) and the seventh plague (Shemot 9:26).