How does this Pasuk fit into the context of the Parshah? What are the connotations of the word "Ki [Va Sus Pharaoh]"?
Rashi #1: With reference to the following Pasuk, it means that "when the horses of Pharaoh entered the sea...," that is when "Miriam took a drum in her hand..." (15:20). 1
Rashi #2 (in Teshuvos Rashi, 251): It means that Miriam took a drum because the horses of Pharaoh entered the sea.
Ramban #1 (citing the Ibn Ezra): It is an intrinsic part of the Shirah - inasmuch as it relates how Hashem made the water crash down on the Egyptians even while Yisrael were still walking along the dry sea-bed - a miracle within a miracle. In fact, they sang it together with the rest of the Shirah. 2
Ramban #2: It is telling us that they sang the Shirah immediately following the drowning of the Egyptians, not the next day or at a later date.
Ramban #3 and Seforno: It is to inform us that Yisrael sang the Shirah while they were still walking on dry land in the middle of the sea, and not after they had come up. 3
Maharal (Gevuros Hashem, end Ch. 47, p. 194): "There can be no king without a nation." Hence, when adversaries rise up against that nation, it is a challenge to the sovereignty of the king himself; he must therefore arise to save his nation and do battle with the enemy. Hashem is our King, and we are His nation; therefore He fights and destroys our enemies 4 - such as "Pharaoh and his horses, upon whom He let back the waters of the sea." Thus, this Pasuk is a direct continuation of the themes of the Shirah - - the future of Am Yisrael, and the sovereignty of Hashem.
Gur Aryeh understands Rashi's terse comment differently; see 15:19:1.1:1 .
But the Ramban himself maintains that it is not written in the style of a Shirah or a prophecy.
Rambam and Hadar Zekenim: And that that was when Miriam took the drum and read out to the women the first Pasuk of the Shirah for them to repeat after Moshe and the men.
Maharal: As in the Pasuk, "Hashem is King always and forever; the nations were destroyed from His Land" (Tehilim 10:16).
Why does the Torah write "Sus (singular) Pharaoh"?
Refer to 15:1:6 .
What are the ramifications of the Pasuk, "u'Venei Yisrael Halechu ba'Yabashah b'Soch ha'Yam"?
Targum Yonasan: There, in the middle of the sea, there were springs of sweet water and fruit-trees, and vegetables and sweets on the sea-bed. 1
Interestingly, on the same words earlier in the Parshah, in 14:29, Targum Yonasan made no comment; nor does there seem to be anything in the Pasuk to indicate what he writes here.
QUESTIONS ON RASHI
Rashi writes: "'Ki Va ...' - 'Ka'asher Ba' (when they came)." What was unclear about this?
Gur Aryeh: At times, the word "Ki" is translated as "Should it happen that ...," referring to an event in the future (e.g. Bereishis 38:16, Devarim 21:10). But here, it clearly refers to an event that happened already.