The song of Moses, recorded in Exodus 15:1–18, was what Moses and the people of Israel sang after they completed their crossing of the Red Sea (their final escape from Egypt when they saw the Egyptians dead on the seashore). On yonder side of the Red Sea, Moses and the Israelites were clearly “conquerors,” just as the people were who had triumphed over the beast and its image. Hence, their singing of this song. In fact, there are themes in Moses’ song from Exodus 15 that recur in the song the redeemed sing in Revelation 15:3–4.
3 And they sing the song of Moses, the servant of God, and the song of the Lamb, saying, “Great and amazing are your deeds, O Lord God the Almighty! Just and true are your ways, O King of the nations!