662. 15:3 They sing the song of Moses, the servant of God, and the song of the Lamb. This symbolizes a confession springing from charity, thus from a life in accordance with the precepts of the Law contained in the Ten Commandments, and from a faith in the Divinity of the Lord's humanity.
To sing a new song means to joyfully confess from the heart and affection that the Lord alone is the Savior and Redeemer and the God of heaven and earth, as may be seen in nos. 279, 617 above. Here, however, the song is called not a new song, but the song of Moses, the servant of God, and the song of the Lamb; and the song of Moses symbolizes a confession springing from a life in accordance with the precepts of the Law that constitute the Ten Commandments, thus from charity, while the song of the Lamb symbolizes a confession springing from a faith in the Divinity of the Lord's humanity. For the Lamb means the Lord in respect to His Divine humanity (nos. 269, 291, 595), while Moses in a broad sense means all the law written in his five books, and in a strict sense, the Law called the Ten Commandments; and because this serves people in the way they live, the song of Moses is called the song of Moses, the servant of God. For in the Word a servant means someone or something that serves (no. 380), in this case for the way one is to live.
 Moses in a broad sense is called the Law because his five books are called the Law. All the commandments, judgments and statutes given through him in his five books are called the Law, as may be seen in no. 417 above. That everything written in those books is called Moses and the Law of Moses can be seen from the following passages:
Philip... said..., "We have found Him of whom Moses in the Law, and of whom the prophets, wrote, Jesus...." (John 1:45)
In the law Moses commanded us to stone such. (John 8:5)
...the days of their purification according to the Law of Moses were completed... (Luke 2:22)
...all things must be fulfilled which were written in the Law of Moses and the Prophets... concerning Me. (Luke 24:44, cf. 24:27)
Did not Moses give you the Law? ...Moses... gave you circumcision... so that the Law of Moses should not be broken... (John 7:19, 22-23)
Abraham said to (the rich man in hell), "They have Moses and the prophets; let them hear them... If they do not hear Moses and the prophets, neither will they be persuaded if someone should rise from the dead." (Luke 16:29, 31)
The curse and the oath written in the Law of Moses the servant of God has been poured out on us... As it is written in the Law of Moses, all this evil has come upon us. (Daniel 9:11, 13)
Remember the Law of Moses, My servant, which I commanded him... (Malachi 4:4)
Jehovah said to Moses, "Behold, I will come to you in the mist of a cloud, that the people may hear when I speak with you, and also believe you forever." (Exodus 19:9)
 It can be seen from this that Moses in a broad sense means the Word written by him, called the Law. That Moses means the Law that constitutes the Ten Commandments also then follows, and the more so because Moses hewed out the tablets after he broke the first ones (Exodus 34:1, 4); and when he brought them down, his face shone (Exodus 34:29-35). That is why Moses in paintings is depicted holding the tablets in his hand. Moreover, we are told in Mark, "Moses said, Honor your father and your mother" (Mark 7:10). And Joshua "wrote on the stones (of the altar) a copy of the Law of Moses" (Joshua 8:32). That Law was the Ten Commandments.
It can be seen from this that in the present case, the song of Moses, the servant of God, means nothing else than a confession springing from charity, thus from a life in accordance with the precepts of the Law contained in the Ten Commandments.