Expositor's Bible Commentary Commentary Revelation 15:3

"And they sing the song of Moses the servant of God, and the song of the Lamb, saying, Great and marvellous are thy works, O Lord God, the Almighty; righteous and true are thy ways, thou King of the ages." — Revelation 15:3 (ASV)

The song sung by the redeemed is the “song of Moses, the servant of God and the song of the Lamb”—a single song as vv.3–4 show. The Song of Moses is in Ex 15:1–18. It celebrated the victory of the Lord in the defeat of the Egyptians at the Red Sea. In the ancient synagogue it was sung in the afternoon service of each Sabbath to celebrate God’s sovereign rule over the universe, of which the redemption from Egypt reminded the Jew. As the deliverance from Egypt, with its plagues of judgment on Israel’s enemies, became for the Jew a signpost of God’s just rule over the world, so God’s final judgment and the deliverance of the followers of the Lamb bring forth from the victors over the beast exuberant songs of praise to God for his righteous acts in history.

Each line in vv.3–4 picks up phrases from the Psalms and Prophets. Compare the following OT words with vv.3–4: “Then Moses and the Israelites sang this song” (Exodus 15:1); “your works are wonderful” (Psalms 139:14); “LORD God Almighty” (Amos 4:13); “all his ways are just. A faithful God... upright and just is he” ; “who shall not revere you, O King of the nations” (Jeremiah 10:7); “they will bring glory to your name” (Psalms 86:9), etc. John may or may not have heard the victors over the beast singing these actual words. But it was revealed to him that they were praising God for his mighty deliverance and for judgment on their enemies.