September 8. On this date in 1964, the Universal House of Justice wrote "the beloved Guardian was not only a translator but the inspired Interpreter of the Holy Writings; thus, where a passage in Persian or Arabic could give rise to two different expressions in English he would know which one to convey. Similarly he would be much better equipped than an average translator to know which metaphor to employ in English to express a Persian metaphor which might be meaningless in literal translation."

September 8. On this date in 1964, the Universal House of Justice wrote "the beloved Guardian was not only a translator but the inspired Interpreter of the Holy Writings; thus, where a passage in Persian or Arabic could give rise to two different expressions in English he would know which one to convey. Similarly he would be much better equipped than an average translator to know which metaphor to employ in English to express a Persian metaphor which might be meaningless in literal translation."

The Universal House of Justice
Bahá'í World Centre
Department of the Secretariat
16 September 1992
Dear Bahá'í Friend,
The questions contained in your letter to ... about the language of Revelation and the status of Shoghi Effendi's translations were referred to the Universal House of Justice. We are instructed to convey the following response.
With respect to your inquiry about whether, in the Bahá'í context, English might possibly be regarded as a language of Revelation, the House of Justice asks us to explain that, while Shoghi Effendi's translations of the Writings of Bahá'u'lláh into English carry with them a large measure of interpretation of the intent and purpose of the Author of the text -- an interpretation which he, as Interpreter of the Sacred Text, could alone authoritatively provide -- one should not conclude that the English language into which the Writings were translated could, therefore, be considered as a language of Revelation.
As to the special status of Shoghi Effendi's translations, the beloved Guardian in a letter dated 15 November 1956 written on his behalf specified that "this English translation" of a Text should form the "basis" for translations into other European languages. The Universal House of Justice, in a letter of 8 September 1964 underlined the uniqueness of the translations of Shoghi Effendi and provided the following elucidation:

...the beloved Guardian was not only a translator but the inspired Interpreter of the Holy Writings; thus, where a passage in Persian or Arabic could give rise to two different expressions in English he would know which one to convey. Similarly he would be much better equipped than an average translator to know which metaphor to employ in English to express a Persian metaphor which might be meaningless in literal translation.

Thus, in general, speakers of other European tongues will obtain a more accurate translation by following the Guardian's English translation than by attempting at this stage in Bahá'í history to translate directly from the original.
This does not mean, however, that the translators should not also check their translation with the original texts if they are familiar with Persian or Arabic. There may be many instances where the exact meaning of the English text is unclear to them and this can be made evident by comparison with the original....
The Universal House of Justice has also clarified that while the English translations of the Guardian might serve as a useful resource, translations into Oriental languages such as Turkish and Urdu could be made directly from the original texts.
We are asked to assure you of the prayers of the Universal House of Justice for the confirmation of your services to the Cause of God.
With loving Bahá'í greetings,
For Department of the Secretariat, ...

To summarize rules of Bahá'í translations...

Arabic works cannot be translated into Persian.

Persian works cannot be translated into Arabic.

Persian and Arabic works can be translated "into Oriental languages such as Turkish and Urdu."

Persian and Arabic works can be translated into English.

Persian and Arabic works cannot be translated into non-English "European languages."

English works can be translated into non-English "European languages."

For further reading, please see "Persian, Arabic, and Provisional Translations", "Translation and provisional translations", "Unveiling the Hidden Words, by Diana Malouf: Commentary on "Translating the Hidden Words,' review by Franklin Lewis", a letter dated June 27, 1933 from Shoghi Effendi to Adelbert Mühlschlegel about Bahá'í orthography, a letter dated June 30, 1999 from the Universal House of Justice outlining its procedures for approving provisional as opposed to authorized translations, and a letter dated February 15, 1957 from Shoghi Effendi to French Bahá'ís.