Ps 149:1

“Let us praise the Lord both in voice, and in understanding, and in good works; and, as this Psalm exhorteth, let us sing unto Him a new song. It beginneth: "Sing ye to the Lord a new song. His praise is in the Church of the Saints" (ver. 1). The old man hath an old song, the new man a new song. The Old Testament is an old song, the New Testament a new song. In the Old Testament are temporal and earthly promises. Whoso loveth earthly things singeth an old song: let him that desireth to sing a new song, love the things of eternity. Love itself is new and eternal; therefore is it ever new, because it never groweth old. ...And this song is of peace, this song is of charity. Whoso severeth himself from the union of the saints, singeth not a new song; for he hath followed old strife, not new charity. In new charity what is there? Peace, the bond of an holy society, a spiritual union, a building of living stones. Where is this? Not in one place, but throughout the whole world. This is said in another Psalm, "Sing unto the Lord, all the earth." From this is understood, that he who singeth not with the whole earth, singeth an old song, whatever words proceed out of his mouth. ...We have already said, brethren, that all the earth singeth a new song. He who singeth not with the whole earth a new song, let him sing what he will, let his tongue sound forth Halleluia, let him utter it all day and all night, my ears are not so much bent to hear the voice of the singer, but I seek the deeds of the doer. For I ask, and say, "What is it that thou singest?" He answereth, "Halleluia." What is "Halleluia"? "Praise ye the Lord." Come, let us praise the Lord together. If thou praisest the Lord, and I praise the Lord, why are we at variance? Charity praiseth the Lord, discord blasphemeth the Lord." ...”

“O brothers, o sons, o Catholic offspring, o holy and celestial seeds, o regenerated in Christ and born from above, listen to me, rather through me: Sing to the Lord a new song. "Look," you say, "I sing." You sing, indeed you sing, I hear. But let life not contradict the testimony of the tongue. Sing with voices, sing with hearts, sing with mouths, sing with lifestyles: Sing to the Lord a new song. Are you asking what you should sing about him whom you love? Without a doubt, you want to sing about him whom you love. You seek his praises to sing. You have heard: Sing to the Lord a new song. Are you seeking praises? His praise is in the congregation of the saints. The praise of singing is the singer himself. Do you want to speak praises to God? Be yourselves what you say. You are his praise if you live well. For his praise is not in the synagogues of the Jews, not in the madness of the pagans, not in the errors of the heretics, not in the applause of the theaters. Are you looking for where it is? Pay attention, be yourselves: His praise is in the congregation of the saints.”