The Sages taught: On that same day, Rabbi Akiva taught that at the time that the Jewish people ascended from the Sea [of Reeds], they set their eyes on saying a song. And how did they say the song? Like an adult reciting Hallel, and [the congregation] repeats after him the chapter headings. Moses said: “I will sing to the LORD” (Ex. 15:1), and [the people] said: “I will sing to the LORD.” Moses said: “For He has triumphed gloriously” (Ex. 15:1), and they said: “I will sing to the LORD.” Rabbi Eliezer, son of Rabbi Yosei HaGelili, says: [At the sea, they sang] like a minor reciting Hallel and [the congregation] repeats after him all that he says. Moses said: “I will sing to the Lord” (Ex. 15:1), and [the people] said: “I will sing to the LORD.” Moses said: “For He has triumphed gloriously,” and they said “For He has triumphed gloriously.” Rabbi Neḥemya says: [At the sea, they sang] like a scribe who leads the Shema in the synagogue; as he begins [with the] first [words of the blessing], and they repeat after him. What are they disagreeing about? Rabbi Akiva holds that “saying” [refers] to the first words. And Rabbi Eliezer, son of Rabbi Yosei HaGelili, holds that “saying” [refers] to each and every word. And Rabbi Neḥemya holds that “they said” [means that] that everyone recited together, and “saying” [means] that Moses began first.

“They said, saying:” to [future] generations, to require that they say this song daily, every day.

“They said, saying:” the “saying” is doubled just as the language of the entire Song is doubled, since throughout all the verses of the song all its themes are doubled, and you will find the same in Hallel, i.e., “In distress I called on the LORD / and the LORD answered and brought me relief” (Ps. 118:5) up to “This is the day that the LORD has made” (v. 24) - all the language is doubled. And this doubling of praise is a hint that there is one [type of divine] power layered over another, and that is why the Song is written with doubled language. Certain praises are addressed to the attribute of mercy and to the Divine Presence, [such as] “I will sing to the LORD” (Ex. 15:1) and afterwards “the LORD is my strength and might” (Ex. 15:2); [but also] “the LORD is His name” (Ex. 15:3) and afterwards “Your right hand, O LORD” (Ex. 15:6), which represents the attribute of justice....