Hashem will fight for you, but you shall remain silent. (14:13) To understand, What is the meaning of being silent? We find in the Mishna Sanhedrin 39a that teaches: Therefore, since all humanity descends from one person, each and every person is obligated to say: The world was created for me. But be aware, that it is stated: "When the wicked perish, there is song" (Mishlei 11:10)? The Gemara asks: But is Hashem, Blessed be He, gladdened by the downfall of the wicked? Isn’t it written in the verse describing the victory of the Jewish people in battle: "He appointed them that should sing unto the Lord, and praise in the beauty of holiness, as they went out before the army, and say: Give thanks to the Lord, for His mercy endures forever” (Divrei Hayamim 2 20:21). And Rabbi Yonoson asks: Why is it not stated in this praise: “Give thanks to the Lord for He is good, for His mercy endures forever,” as is stated elsewhere (Tehilim 118:1)? This is because the Hashem Blessed be He, is not gladdened by the downfall of the wicked.
The Gemara comments: As Rabbi Shmuel bar Nachman says that Rabbi Yonoson says: What is the meaning of that which is written in the passage describing the splitting of the Red Sea: "And the one came not near the other all the night” (Shemos 14:20)? At that time the ministering angels desired to recite a song before the Hashem. Hashem Blessed be He, said to them: My handiwork the Egyptians, are drowning in the sea, and you are reciting a song before Me? Apparently, Hashem is not gladdened by the downfall of the wicked.
It is interesting to note what is brought in Gemara Sanhedrin 95b. King Sancheriv came with a vast army to conquer Jerusalem. When he saw how small the city was, he said we have time to wait until tomorrow. In the meantime let us rest up and in the morning we shall conquer the city. The Navi states in Yeshaya 37:36: "Then the angel of the Lord went forth and inflicted a heavy blow on in the camp of the Assyrians one hundred and eighty-five thousand. And when they arose early in the morning, behold, they were all dead corpses”. The sages discuss how did they all die so quickly? Rabbi Yitzchak Nafcha says: Hashem revealed ears for them and they were able to hear the songs of praise from the mouths of the heavenly angels drawing the chariot of Hashem, and they died, as it is stated: “From Your exaltation the nations were scattered” (Yeshaya 33:3), indicating that their death was caused by the revelation of the angels praising Hashem’s greatness.
Based on this Gemarra we can ask why did Hashem have to punish the Egyptians by drowning them in the sea, when there could have been a simpler solution? When the Egyptians came forth with their army, Hashem could have opened their ears to hear the song of the angels, and the Egyptians would perish the same way as the army of Sancheriv had perished?
However, we just brought the Gemarra Sanhedrin 39a that the angels wanted to say Shira, and Hashem forbid them, saying “My handiwork, the Egyptians, are drowning in the sea, and you are reciting a song before Me?” Then we have to ask the question, Why then did Hashem allow the angels to say Shira by Sancheriv? The answer is that we can interpret the words of the Gemarra as follows: Hashem was telling the angels, since the Egyptians were guilty of drowning the Jewish children, they have to be punished measure for measure. Therefore, the punishment had to be that they drown in the sea. Whereas, by Sancheriv they could be punished by hearing the Shira of the angels.
This is the insight to our Posuk: Hashem will fight for you, but you shall remain silent. Hashem is commanding the angels to be silent and not to recite the Shira in order to kill the Egyptians, as by Sancheriv. Because in this case, Hashem has to punish measure for measure with drowning them.
We can now explain: Then Moshe and the children of Israel sang this song to Hashem, and they spoke, saying, I will sing to Hashem, for very exalted is He; a horse and its rider He cast into the sea. The word “Then” means after the angels were quiet in order to deal the punishment to the Egyptians, and “a horse and its rider He cast into the sea”, now it was spontaneous for Moshe and Klal Yisrael to praise Hashem with Shira “because He is very exalted”. The Egyptians were punished, and Klal Yisrael were rescued from bondage.
(Yehuda Z. Klitnick)