To Darius, His Son, and a Member of Christ, Augustine, a Servant of Christ and of the Members of Christ, Sends Greeting in the Lord.
1. You requested an answer from me as a proof that I had gladly received your letter. Behold, then, I write again; and yet I cannot express the pleasure I felt, either by this answer or by any other, whether I write briefly or at the utmost length, for neither by few words nor by many is it possible for me to express to you what words can never express. I, indeed, am not eloquent, though ready in speech; but I could by no means allow any man, however eloquent, even though he could see as well into my mind as I do myself, to do that which is beyond my own power, viz. to describe in a letter, however able and however long, the effect which your epistle had on my mind. It remains, then, for me so to express to you what you wished to know, that you may understand as being in my words that which they do not express. What, then, shall I say? That I was delighted with your letter, exceedingly delighted—the repetition of this word is not a mere repetition, but, as it were, a perpetual affirmation; because it was impossible to be always saying it, therefore it has been at least once repeated, for in this way perhaps my feelings may be expressed.
Source: Letters (New Advent)