The Mekhilta interprets the phrase "For He is high on high" (Exodus 15:1) as describing a relationship of mutual exaltation between God and Israel. The doubling in the Hebrew — ga'oh ga'ah, "high on high" — suggests two acts of elevation: He exalted me, and I exalted Him. God and Israel lifted each other up, each responding to the other's praise with greater praise in return.
The Mekhilta traces the pattern back to Egypt. God exalted Israel in Egypt by declaring: "My first-born son is Israel" (Exodus 4:22). Before the plagues began, before the sea split, God elevated an enslaved people to the status of His own firstborn child. That was God's act of exaltation — claiming the lowest of the low as His most precious possession.
Israel reciprocated. They exalted God in Egypt through their observance of Pesach, the festival of liberation. The prophet Isaiah captures this: "The song will be for you as on the night of the sanctification of the festival, and rejoicing of heart as one going with flute to come to the mountain of the Lord, to the Rock of Israel" (Isaiah 30:29). Israel's celebration of Pesach — their singing, their joy, their pilgrimage — was their way of lifting God's name before the nations.
The Song of the Sea, then, is not a one-directional hymn of praise. It is the climactic moment in a back-and-forth exchange that began in Egypt. God called Israel His firstborn. Israel called God their Rock. Each act of exaltation invited a greater one in return.