6 What follows because the Salvation of God is known in all nations? “Let the peoples confess to You, O God”; “confess to You,” he says, “all peoples.” There stands forth a heretic, and he says, In Africa I have peoples: and another from another quarter, And I in Galatia have peoples. You in Africa, he in Galatia: therefore I require one that has them everywhere. You have indeed dared to exult at that voice, when you heard, “Let the peoples confess to You, O God.” Hear the following verse, how he speaks not of a part: “Let there confess to You all peoples.”
Walk ye in the Way together with all nations; walk ye in the Way together with all peoples, O sons of peace, sons of the One Catholic Church, walk ye in the Way, seeing as you walk. Wayfarers do this to beguile their toil. Sing ye in this Way; I implore you by that Same Way, sing ye in this Way: a new song sing ye, let no one there sing old ones: sing ye the love-songs of your fatherland, let no one sing old ones. New Way, new wayfarer, new song. Hear thou the Apostle exhorting you to a new song: “Whatever therefore is in Christ is a new creature; old things have passed away, behold they have been made new.”
A new song sing ye in the way, which you have learned “on the earth.” In what earth? “In all nations.” Therefore even the new song does not belong to a part. He that in a part sings, sings an old song: whatever he please to sing, he sings an old song, the old man sings: divided he is, carnal he is. Truly in so far as carnal he is, so far he is old; and in so far as he is spiritual, so far new. See what says the Apostle: “I could not speak to you as if to spiritual, but as if to carnal.” Whence proves he them carnal?
“For while one says, I am of Paul; but another, I of Apollos: are you not,” he says, “carnal?” Therefore in the Spirit a new song sing thou in the safe way. Just as wayfarers sing, and ofttimes in the night sing. Awful round about all things do sound, or rather they sound not around, but are still around; and the more still the more awful; nevertheless, even they that fear robbers do sing. How much more safely you sing in Christ! That way has no robber, unless thou by forsaking the way fallest in the hands of a robber....Why fear ye to confess, and in your confession to sing a new song together with all the earth; in all the earth, in Catholic peace, do you fear to confess to God, lest He condemn you that hast confessed?
If having not confessed you lie concealed, having confessed you will be condemned. You fear to confess, that by not confessing can not be concealed: you will be condemned if you have held your peace, that might have been delivered, by having confessed. “O God, confess to You all peoples.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)