The text below is from a sermon by Saint Augustine (354-430 AD)
Sing to the Lord a new song; his praise is in the assembly of the saints. We are urged to sing a new song to the Lord, as new men who have learned a new song. A song is a thing of joy; more profoundly, it is a thing of love. Anyone, therefore, who has learned to love the new life has learned to sing a new song, and the new song reminds us of our new life. The new man, the new song, the new covenant, all belong to the one kingdom of God, and so the new man will sing a new song and will belong to the new covenant.
There is not one who does not love something, but the question is, what to love. The psalms do not tell us not to love, but to choose the object of our love. But how can we choose unless we are first chosen? We cannot love unless someone has loved us first. Listen to the apostle John: We love him, because he first loved us. The source of man’s love for God can only be found in the fact that God loved him first. He has given us himself as the object of our love, and he has also given us its source. What this source is you may learn more clearly from the apostle Paul who tells us: The love of God has been poured into our hearts. This love is not something we generate ourselves; it comes to us through the Holy Spirit who has been given to us.
Since we have such an assurance, then, let us love God with the love he has given us. As John tells us more fully: God is love, and whoever dwells in love dwells in God, and God in him. It is not enough to say: Love is from God. Which of us would dare to pronounce the words of Scripture: God is love? He alone could say it who knew what it was to have God dwelling within him. God offers us a short route to the possession of himself. He cries out: Love me and you will have me for you would be unable to love me if you did not possess me already.
My dear brothers and sons, fruit of the true faith and holy seed of heaven, all you who have been born again in Christ and whose life is from above, listen to me; or rather, listen to the Holy Spirit saying through me: Sing to the Lord a new song. Look, you tell me, I am singing. Yes indeed, you are singing; you are singing clearly, I can hear you. But make sure that your life does not contradict your words. Sing with your voices, your hearts, your lips and your lives: Sing to the Lord a new song.
Now it is your unquestioned desire to sing of him whom you love, but you ask me how to sing his praises. You have heard the words: Sing to the Lord a new song, and you wish to know what praises to sing. The answer is: His praise is in the assembly of the saints; it is in the singers themselves. If you desire to praise him, then live what you express. Live good lives, and you yourselves will be his praise.