שמות טו ,א: כּ י־גָאֹה גָ אָה סוּס וְרֹכְבוֹ רָמָה בַיָם
The Sforno interprets the song of praise to HaShem as the first recognizing His triumph over Paroh, the King; secondly over the army and its captains; and finally over the multitude of Egypt and their chariots. Therefore, he interprets the phrase “the horse and his rider” as referring to Paroh. The reason it is necessary to stress this victory over Paroh who had boastfully claimed to be a deity who possessed great power and was a great king to whom even other kings were subservient. The downfall of Paroh and the great miracle of the dividing of the waters established the supremacy of HaShem and refuted the absurd claims of the king of Egypt.