Vaera #1: Spitting blood and whistling frogs - the tzadi - kuf switchoff

There are two midrashim in this week's parsha that make use of a tzadi - quf switch. The tzadi, quf, ayin, and tet are emphatic consonants, and we sometimes see switchoffs between members of this group. For example, there is an in-between emphatic consonant in the word ארץ that shows up as צ in Hebrew but ע in Aramaic (thus ארעא). At one time, a ק appears, making ארק. One midrash has the whistling frog:

Midrash Rabba Shemot parasha 10:
וַתַּעַל הַצְּפַרְדֵּעַ וַתְּכַס אֶת וגו' תני רבי עקיבא אומר צפרדע אחת היתה והיא
השריצה ומלאה את ארץ מצרים אמר לו רבי אלעזר בן עזריה עקיבא מה לך אצל הגדה כלה מדברותיך ולך אצל נגעים ואהלות צפרדע אחת היתה ושרקה להן ובאו.

Shemot 7:27-28

וְאִם-מָאֵן אַתָּה, לְשַׁלֵּחַ: הִנֵּה אָנֹכִי, נֹגֵף אֶת-כָּל-גְּבוּלְךָ--בַּצְפַרְדְּעִים.
וְשָׁרַץ הַיְאֹר, צְפַרְדְּעִים, וְעָלוּ וּבָאוּ בְּבֵיתֶךָ, וּבַחֲדַר מִשְׁכָּבְךָ וְעַל-מִטָּתֶךָ; וּבְבֵית עֲבָדֶיךָ וּבְעַמֶּךָ, וּבְתַנּוּרֶיךָ וּבְמִשְׁאֲרוֹתֶיךָ

"And if thou refuse to let them go, behold, I will smite all thy borders with frogs.
And the river shall swarm with frogs, which shall go up and come into thy house, and into thy bed-chamber, and upon thy bed, and into the house of thy servants, and upon thy people, and into thine ovens, and into thy kneading-troughs."

Shemot 8:2-4:

וַיֵּט אַהֲרֹן אֶת-יָדוֹ, עַל מֵימֵי מִצְרָיִם; וַתַּעַל, הַצְּפַרְדֵּעַ, וַתְּכַס, אֶת-אֶרֶץ מִצְרָיִם.
וַיַּעֲשׂוּ-כֵן הַחַרְטֻמִּים, בְּלָטֵיהֶם; וַיַּעֲלוּ אֶת-הַצְפַרְדְּעִים, עַל-אֶרֶץ מִצְרָיִם.
וַיִּקְרָא פַרְעֹה לְמֹשֶׁה וּלְאַהֲרֹן, וַיֹּאמֶר הַעְתִּירוּ אֶל-יְהוָה, וְיָסֵר הַצְפַרְדְּעִים, מִמֶּנִּי וּמֵעַמִּי; וַאֲשַׁלְּחָה, אֶת-הָעָם, וְיִזְבְּחוּ, ה.

"And Aaron stretched out his hand over the waters of Egypt; and the frogs came up, and covered the land of Egypt.
And the magicians did in like manner with their secret arts, and brought up frogs upon the land of Egypt.
Then Pharaoh called for Moses and Aaron, and said: 'Entreat the LORD, that He take away the frogs from me, and from my people; and I will let the people go, that they may sacrifice unto the LORD.'"

'And the frog[s] came up, and (it) covered, etc'. A brayta (See Sanhedrin page 67): R Akiva says, a single frog there was and she multiplied and filled the land of Egypt.

Rabbi Elazar ben Azarya said to him, Akiva, what have you to do with Haggada? End your words and go to (the Laws) of (the impurities) of Skin Ailments and Tents. (Rather,) there was a single frog and she whistled to them and they came.

The impetus for the midrash is that Moshe promises many frogs, but in Shemot 8:2 we read that הַצְּפַרְדֵּעַ, the frog, came up, וַתְּכַס, and she covered the land. Then we read of many frogs. A pshat explanation is that הַצְּפַרְדֵּעַ is a collective noun, referring to a group in the singular. R Akiva gives one midrashic explanation how one frog became many, and R Elazar ben Azarya offers another. What, though, is the basis for the whistling frog?

Well, the verb is שרקה, whistled. I would claim there is a drash from Sharatz, with the emphatic Tzadi switching with the emphatic Kuf. R Akiva says צפרדע אחת היתה והיא השריצה, there was one frog and she hishritza, multiplied. R Elazar ben Azarya says צפרדע אחת היתה ושרקה להן ובאו, there was one frog and she sharqa, whisted. This would be based on the earlier pasuk, in which Moshe promised: וְשָׁרַץ הַיְאֹר, צְפַרְדְּעִים, וְעָלוּ וּבָאוּ בְּבֵיתֶךָ.

Another midrash claims that all the water in Egypt turned to blood - even the spittle of the Egyptians. The source of this is Shemot 7:19:

יט וַיֹּאמֶרה אֶל-מֹשֶׁה, אֱמֹר אֶל-אַהֲרֹן קַח מַטְּךָ וּנְטֵה-יָדְךָ עַל-מֵימֵי מִצְרַיִם עַל-נַהֲרֹתָם עַל-יְאֹרֵיהֶם וְעַל-אַגְמֵיהֶם וְעַל כָּל-מִקְוֵה מֵימֵיהֶם--וְיִהְיוּ-דָם; וְהָיָה דָם בְּכָל-אֶרֶץ מִצְרַיִם, וּבָעֵצִים וּבָאֲבָנִים.

19 And the LORD said unto Moses: 'Say unto Aaron: Take thy rod, and stretch out thy hand over the waters of Egypt, over their rivers, over their streams, and over their pools, and over all their ponds of water, that they may become blood; and there shall be blood throughout all the land of Egypt, both in vessels of wood and in vessels of stone.'

It seems fairly clear that what the midrash is doing is reading the phrase אֶרֶץ מִצְרַיִם as if it were רק מצריים, the spittle of the Egyptians. This is another tzadi - quf switchoff.