On September 30, 1943, His Holiness Pope Pius XII issued his now famous encyclical on scripture studies, Divino afflante Spiritu. He wrote: “We ought to explain the original text which was written by the inspired author himself and has more authority and greater weight than any, even the very best, translation whether ancient or modern. This can be done all the more easily and fruitfully if to the knowledge of languages be joined a real skill in literary criticism of the same text.”
Early in 1944, in conformity with the spirit of the encyclical, and with the encouragement of Archbishop Cicognani, Apostolic Delegate to the United States, the Bishops’ Committee of the Confraternity of Christian Doctrine requested members of The Catholic Biblical Association of America to translate the sacred scriptures from the original languages or from the oldest extant form of the text, and to present the sense of the biblical text in as correct a form as possible.
The work of translating the Bible has been characterized as “the sacred and apostolic work of interpreting the word of God and of presenting it to the laity in translations as clear as the difficulty of the matter and the limitations of human knowledge permit” (A. G. Cicognani, Apostolic Delegate, in The Catholic Biblical Quarterly, 6, , 389-90). In the appraisal of the present work, it is hoped that the words of the encyclical Divino afflante Spiritu will serve as a guide: “Let all the sons of the church bear in mind that the efforts of these resolute laborers in the vineyard of the Lord should be judged not only with equity and justice but also with the greatest charity; all moreover should abhor that intemperate zeal which imagines that whatever is new should for that very reason be opposed or suspected.”
From: The Preface to the New American Bible
New translations and revision of existing translations are required from time to time for various reasons.
For example, it is important to keep pace with the discovery and publication of new and better ancient manuscripts (e.g., the Dead Sea scrolls) so that the best possible textual tradition will be followed, as required by Divino afflante spiritu.
There are advances in linguistics of the biblical languages which make possible a better understanding and more accurate translation of the original languages.
And there are changes and developments in vocabulary and the cultural background of the receptor language. An obvious example of this is the abandonment in English of the second person singular (use of “thee,” “thou,” “sayest,” “hearest”), which had a major impact on Bible translations.
Other changes are less obvious but are nevertheless present. There have been changes in vocabulary; for example, the term “holocaust” is now normally reserved for the sacrilegious attempt to destroy the Jewish people by the Third Reich.
Concerns such as these are reflected in what Pope John Paul II spoke of as the “three pillars” of good biblical translation: “A good translation is based on three pillars that must contemporaneously support the entire work. First, there must be a deep knowledge of the language and the cultural world at the point of origin. Next, there must be a good familiarity with the language and cultural context at the point where the work will arrive. Lastly, to crown the work with success, there must be an adequate mastery of the contents and meaning of what one is translating”—and he praised the translation that “utilizes the vocabulary and idioms of everyday speech” (“le parole e le forme della lingua di tutti i giorni”). (From an address to the United Bible Societies, November 26, 2001.)
My understanding is that the Bishops were asked to revise the NAB. It was desirable to have a new translation that was based on the very earliest sources available (Hebrew, Greek, Aramaic) and to have a more literal translation.