Commento su Esodo 15:19

כי בא סוס פרעה means WHEN [THE HORSES] CAME.

FOR THE HORSES OF PHARAOH WENT IN WITH HIS CHARIOTS AND WITH HIS HORSEMEN. Rabbi Abraham ibn Ezra said that this verse is also part of the Song, for Moses and the children of Israel were singing and saying: For the horses of Pharaoh went in with his chariots and with his horsemen into the sea, and the Eternal brought back the waters of the sea upon them while the children of Israel were walking on dry land in the midst of the sea, this being a miracle within a miracle.²³²For when the horses of Pharaoh went in, etc., He brought the waters upon them, and at the same time, the children of Israel walked on dry land.
But this verse is not written in the style of the Song, nor is it in the style of prophecies! [Therefore, Ibn Ezra’s interpretation is not correct.] Instead, the verse is to be interpreted [as dating the Song]: Then sang Moses — when the horses of Pharaoh went in. Immediately on that day — not the following day or at some later time — [he sang this Song]. It may be that the sense thereof is as follows: Then Moses sang, when the horses of Pharaoh went into the sea and G-d brought back the waters of the sea upon them while the children of Israel were yet walking on dry land in the midst of it. Thus the verse relates that they said the Song while they were walking in the midst of the sea on dry land. Scripture further tells²³³Verses 20-21. that it was then that Miriam the prophetess took the timbrel in hand and sang them the first verse of the Song that they, [i.e., the women], should sing after Moses and Israel.

כי בא סוס פרעה, the opening words of this song,אז ישיר משה had been inspired by the spectacle of Pharaoh with his chariot, his horses and its riders drowning in the sea at the time when the Israelites, by contrast, were taking their time walking through the same sea on dry ground. ביבשה בתוך הים, they began the song of thanksgiving even before all had emerged from the sea to the shore.