1 When the Holy Gospel was being read, we heard that the Lord Jesus exulted in Spirit, and said, “I confess to You, O Father, Lord of heaven and earth, for that You have hid these things from the wise and prudent, and hast revealed them unto babes.” Thus much to begin with, we find before we pass on further, if we consider the words of the Lord with due attention, with diligence, and above all with piety, that we ought not invariably to understand when we read of “confession” in the Scriptures, the confession of a sinner.
Now special need there was of saying this, and of reminding you, Beloved, of this, because as soon as this word was uttered by the reader's voice, there followed upon it the sound of the beating of your breasts, when you had heard, I mean, what the Lord said, “I confess to You, O Father.” At the uttering of these words, “I confess,” ye beat your breasts. Now what means this beating of the breast, but to show that which lies hid within the breast, and to chastise by the visible beating the secret sin?
And why did ye this, but because ye heard, “I confess to You, O Father.” You heard the words “I confess,” but you did not consider, who it is that confesses. But consider now. If Christ, from whom all sin is far removed, said, “I confess:” confession does not belong to the sinner only, but sometimes to him also that praises God. We confess then, whether in praising God, or accusing ourselves. In either case it is a godly confession, either when you blame yourself, who art not without sin, or when you praise Him who can have no sin.
Source: Sermons on Selected Lessons of the New Testament (New Advent)