Augustine: Sirach's Prophetic Character Uncertain

Moreover, I do not seem to have correctly called prophetic the words in this passage: "Why is earth and ashes proud?" [Sirach 10:9] for the book in which this is read is not the work of one whom we can be certain that he should be called a prophet. Augustine, Retractions, Section 3 of the Retractions regarding On Genesis Against the Manicheans, p. 43, The Fathers of the Church, Volume 60, Sister M. Inez Bogan, R.S.M. translator.