וַיָּשֻׁ֣בוּ הַמַּ֗יִם וַיְכַסּ֤וּ אֶת־הָרֶ֙כֶב֙ וְאֶת־הַפָּ֣רָשִׁ֔ים לְכֹל֙ חֵ֣יל פַּרְעֹ֔ה הַבָּאִ֥ים אַחֲרֵיהֶ֖ם בַּיָּ֑ם לֹֽא־נִשְׁאַ֥ר בָּהֶ֖ם עַד־אֶחָֽד׃
И вернулись воды, и накрыли колесницы и всадников, и все войско фараоново, которое вошло за ними в море; осталось не так много, как один из них.
Rashi
ויכסו את הרכב ... לכל חיל פרעה AND COVERED THE CHARIOTS … AND ALL THE FORCES OF PHARAOH — in regard to the ל of לכל, this is the way of Scripture verses (of Biblical Hebrew) to write a redundant ל, as in (Exodus 27:3) “all (לכל) its vessels shalt thou make of copper”.. So, too, (Exodus 27:19) ‘‘all (לכל) the vessels of the dwelling in all the service thereof”; (Numbers 4:32) “and their pins and their cords and all (לכל) their vessels”. It is only an elegancy of style.
Be'er Mayim Chaim
The waters returned and covered the chariots, etc. including Pharaoh’s entire army, etc. not one of them remained: At first glace, this is repetitive language. After it stated, "including the entire army, etc.," why did it repeat and state, "[none] remained, etc.?" Indeed, however, Scripture is reporting an amazing miracle with this. For have we not already written that the return of the water was while Israel was still in the sea and the sea was split into pieces, such that in one part, He brought through the Israelites within it; and in another part, 'He hurled Pharaoh and his army, etc.!' And that is why the splitting of the Red Sea in the words of the Sages, may their memory be blessed, is always called difficult. Like they said (Sotah 2a), "Pairing them up is as difficult as splitting the Red Sea," and that which is similar to it. All of this is [about] the essence of its splitting, that it was cut into halves. As He made a half, sea; and [the other] half dry land - punishment and mercy - at one instant. And that is difficult before the Holy One, blessed be He - as it is found in the holy Zohar (Vayera 113b), "There was miracle and punishment as one." See there, that it spoke at length about this aspect. And, if so, it comes out that if this was indeed the commandment to the sea - to scramble the Egyptians while the Israelites were still within it - it is certain that it did not delay the words of the Holy One, blessed be He. Rather, immediately when one of the Egyptians came into the sea, the water would come over him and wash him away. Likewise, the second and the third, until the were finished. And such is implied in the statement of the Sages, may their memory be blessed, that we cited above. As they said (Shemot Rabbah 22:2), "When the last of the Israelites ascended from the sea, the last of the Egyptians descended into it." Behold that they were entering one by one; and likewise were they washed away one by one. But, at first glance, how was the understanding of Egypt so wanting and their wisdom so depraved? As the second one saw with his eyes that the first one was washed away into the sea and he yet went in after him, likewise the third and the fourth. However it was already not their will and their intellect that did this. It is like the statement of the Sages, may their memory be blessed (Shir HaShirim Rabbah 1:9:6 on "to a mare in Pharaoh’s chariots"), "The waves of the sea appeared like female horses and [the horses of] Egypt were like aroused stallions, and they pursued them until they sank them in the sea. The Egyptian would say to his horse, 'Yesterday, I would drag you to the Nile and you would not follow me; and now, you are sinking me in the sea?' The horse would say to its rider (Exodus 15:1), '"He cast into the sea (rama bayam)" - see what is in the sea (reu ma bayam),' etc." And that is why it stated, "The waters returned and covered the chariots (a noun form that is usually singular, chariot)." The understanding is that one chariot, the first chariot that came into the sea was washed away; "including Pharaoh’s entire army," which came from behind. That is to say, this was also done to Pharaoh's entire army. Once they came into the sea, they were immediately washed away. And nevertheless, not even "one of them remained," outside. Rather, they all went into the sea, even though they saw the first ones drowning. It was not in the power of the rider to stop the chariot, that it not descend [into the sea]. He was driven against his will and drowned in the depths, as mentioned.
Da'at Zekenim
לא נשאר בהם עד אחד, “not a single one of them remained.” The word עד is sometimes used as inclusive statement whereas other times it is used as exclusion, i.e. in this instance the meaning is that only a single Egyptian survived this drowning. The survivor was Pharaoh himself. We read in Psalms 106,11: אחד מהם לא נותר, “not one of them was left.” How do we reconcile this? The Torah refers to all of Pharaoh’s soldiers having perished. He himself was forced to survive and bear the disgrace of his defeat.