Letter 207: A good speech does more than convey information — it transforms.

To Alypius. How one is to understand: "Unless you turn and become as the little children." [Matthew 18:3] The Lord does not require a reversal of age, a return to being like the little children, as you yourself suppose, like Nicodemus [who took being born again literally, John 3:4], but the denial of vice, so that a childlike simplicity may be present in us. And he shows this by the very words he used, not saying, "Unless you become children," but, "As the little children"; by the addition of the word "as" he indicates the imitation of the thing.

Πῶς νοητέον. «Ἐὰν μὴ στραφῆτε, καὶ γένησθε ὡς τὰ παιδία.» Οὐχ ἡλικίας ὑποστροφὴν τὴν πρὸς τὰ παιδία ὁμοίωσιν ὁ Κύριος ἀπαιτεῖ, ὅπερ αὐτὸς νομίζεις, ὡς ὁ Νικόδημος, ἀλλὰ τῆς κακίας τὴν ἄρνησιν, ὡς παιδιώδη ἡμῖν ἐνυπάρχειν ἁπλότητα. Καὶ τοῦτο δι’ ὧν ἔφησε δείκνυσιν, οὐκ εἰπών, Ἐὰν μὴ γένησθε παιδία, ἀλλ’, Ὡς τὰ παιδία, τῇ τοῦ, ὡς, προσθήκῃ τὴν μίμησιν ἐμφαίνων τοῦ πράγματος.