May 19. On this date in 2015, the Universal House of Justice explained "why such terms as “Alláh-u-Abhá” and “Yá Bahá’u’l-Abhá” are used by Bahá’ís rather than being translated into their native tongues."

May 19. On this date in 2015, the Universal House of Justice explained "why such terms as “Alláh-u-Abhá” and “Yá Bahá’u’l-Abhá” are used by Bahá’ís rather than being translated into their native tongues."

19 May 2015
Dear Bahá’í Friend,
Your email letter of 10 March 2015, asking on behalf of a fellow believer whether it is appropriate to translate the phrase “Alláh-u-Abhá” into another language for purposes of its recitation 95 times a day, has been received at the Bahá’í World Centre and forwarded to our Office for reply. The following has been provided in response to a similar query posed to the Universal House of Justice on a previous occasion:

The Universal House of Justice has received your email letter of 29 December 2008, asking why such terms as “Alláh-u-Abhá” and “Yá Bahá’u’l-Abhá” are used by Bahá’ís rather than being translated into their native tongues, and has asked us to respond as follows.
The House of Justice on another occasion has clarified that the Greatest Name is to be used in its original language for the recitation of “Alláh-u-Abhá” 95 times a day, as well as for its use in the Long Obligatory Prayer and the Prayer for the Dead. It has also clarified that to translate words such as “Alláh-u-Abhá”, “Yá Bahá’u’l-Abhá”, “Mashriqu’l-Adhkár” and “Ḥazíratu’l-Quds” into one’s native language is not acceptable. One exception to this is the alternative use of the words “Right of God” or their equivalent into other languages while the term “Huqúqu’lláh” gradually becomes a part of Bahá’í vocabulary.
In general, one should bear in mind that all translations are, to some degree, inadequate. For instance, the beloved Guardian has pointed out in ... God Passes By that the word “Bahá” signifies at once the “Glory”, the “Splendour” and the “Light” of God; there is no single word in English which can express all these. It is, of course, desirable that there be no loss of meaning through translation; thus, it is preferable that certain terms directly related to the Manifestation of God remain in their original form.
(From a letter dated 22 February 2009 written on behalf of the Universal House of Justice to an individual believer)

With loving Bahá’í greetings,
Office of Correspondence

On February 1, 2018, the Universal House of Justice wrote "That the Arabic Bahá’í Writings are not translated into the Persian language is based on guidance of the beloved Guardian. There are no authorized Persian translations of any of the Arabic Writings, and publication of any Persian translation of the full text of an Arabic Sacred Text is not permitted."

Persian translation of Arabic verses
Universal House of Justice
Transmitted by email
Dear Bahá’í Friend,
1 February 2018
The Universal House of Justice has received your email letter of 7 November 2014 about the translation of the Arabic Writings into Persian. It has considered your questions regarding this matter and has instructed us to write to you as follows. The delay in doing so is deeply regretted.
That the Arabic Bahá’í Writings are not translated into the Persian language is based on guidance of the beloved Guardian. There are no authorized Persian translations of any of the Arabic Writings, and publication of any Persian translation of the full text of an Arabic Sacred Text is not permitted. In his letters to believers in Iran, Shoghi Effendi also exhorted the friends to recite the Obligatory Prayers in Arabic. However, drawing upon an individual’s translation of these Prayers or other Tablets in order to aid one’s understanding is, of course, permissible, although such personal translations should not be recited in Bahá’í gatherings. No issue should be made of what individuals do in private prayer.
Latitude has likewise been given to using a personal translation or a gist of a passage in Persian for the purpose of enhancing understanding of the Writings, and these may be shared for this purpose with a few others — for instance, in the context of a study group. Further, the House of Justice has previously indicated that adding diacriticals to the Arabic words and explaining the meaning of difficult words are also acceptable means of assisting the friends to gain a better understanding of the Writings in Arabic.
In light of a number of factors, Tajik and Persian are for practical purposes treated differently.
It is hoped that the above information will be of assistance. You may rest assured of the loving prayers of the House of Justice at the Sacred Threshold.
With loving Bahá’í greetings,
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 European languages.

English works can be translated into 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.