21 Lastly, would you know what is that Darling? Read the words following: “I will confess unto You, O Lord, in the great Congregation; in a weighty people will I praise You”. Truly says He, “I will confess unto You:” for confession is made in all the multitude, but not in all is God praised: the whole multitude hears our confession, but not in all the multitude is the praise of God. For in all the whole multitude, that is, in the Church which is spread abroad in the whole world, is chaff, and wheat: the chaff flies, the wheat remains; therefore, “in a weighty people will I praise You.” In a weighty people, which the wind of temptation carries not away, in such is God praised. For in the chaff He is ever blasphemed....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)