Come ye, hear, and I will tell, all you that fear God [Psalm 66:16]. Let us come, let us hear, what he is going to tell, "Come ye, hear, and I will tell." But to whom, "Come ye, and hear"? "All you that fear God." If God ye fear not, I will not tell. It is not possible that it be told to any where the fear of God is not. Let the fear of God open the ears, that there may be something to enter in, and a way whereby may enter in that which I am going to tell. But what is he going to tell? "How great things He has done to my soul." Behold, he would tell: but what is he going to tell? Is it perchance how widely the earth is spread, how much the sky is extended, and how many are the stars, and what are the changes of sun and of moon? This creation fulfills its course: but they have very curiously sought it out, the Creator thereof have not known. [Wisdom 13:1] This thing hear, this thing receive, "O you that fear God, how great things He has done to my soul:" if you will, to yours also. "How great things He has done to my soul." "To Him with my mouth I have cried" [Psalm 66:17]. And this very thing, he says, has been done to his soul; that to Him with his mouth he should cry, has been done, he says, to his soul. Behold, brethren, Gentiles we were, even if not in ourselves, in our parents. And what says the Apostle? "You know, when Gentiles you were, to idols without speech how ye went up, being led." [1 Corinthians 12:2] Let the Church now say, "how great things He has done to my soul." "To Him with my mouth I have cried." I a man to a stone was crying, to a deaf stock I was crying, to idols deaf and dumb I was speaking: now the image of God has been turned to the Creator thereof. I that was "saying to a stock, My father you are; and to a stone, You have begotten me:" [Jeremiah 2:27] now say, "Our Father, which art in Heaven." [Matthew 6:9] ..."To Him with my mouth I have cried, and I have exalted Him under my tongue." See how in secret He would be uncorrupt that offers marrowed holocausts. This do ye, brethren, this imitate, so that you may say, "Come ye, see how great things He has done to my soul." For all those things of which he tells, by His Grace are done in our soul. See the other things of which he speaks.
[AD 430] Augustine of Hippo on Psalms 66:16-17