Persian vs Arabic

A word should be said about the style of language in which the Kitáb-i-Aqdas has been rendered into English. Bahá’u’lláh enjoyed a superb mastery of Arabic, and preferred to use it in those Tablets and other Writings where its precision of meaning was particularly appropriate to the exposition of basic principle.

Bahá’u’lláh, The Kitab-i-Aqdas - Universal House of Justice Introduction

Although there can be no question or doubt as to the sweetness of the Persian tongue, yet it hath not the scope of the Arabic. There are many things which have not been expressed in Persian, that is to say, words referring to such things have not been devised, whilst in Arabic there are several words describing the same thing. Indeed there existeth no language in the world as vast and comprehensive as Arabic. This statement is prompted by truth and fairness; otherwise it is clear that in this day the world is being illumined by the splendours of that Sun which hath dawned above the horizon of Persia, and that the merits of this sweet language can scarcely be overestimated.

Bahá’u’lláh, Tabernacle of Unity, par. 2.54-2.58

The distinguished Sáhib hath written: “Since the Beloved in this age is of Persian descent, the Arabic tongue should be abandoned and discarded.” In this connection these sublime words issued from the Pen of the Most High, magnified and exalted be His glory: “Both Arabic and Persian are laudable. That which is desired of a language is that it convey the intent of the speaker, and either language can serve this purpose. And since in this day the Orb of knowledge hath risen in the firmament of Persia, this tongue deserveth every praise.

Bahá’u’lláh, Tabernacle of Unity, par. 2.54-2.58

The Persian tongue is in truth exceedingly sweet and pleasing, and ever since this request was submitted in His most blessed and exalted court, numerous Tablets have been revealed in that language.

Bahá’u’lláh, Tabernacle of Unity, par. 2.54-2.58

Thou hast written concerning languages. Both Arabic and Persian are laudable. That which is desired of a language is that it convey the intent of the speaker, and either language can serve this purpose. And since in this day the Orb of divine knowledge hath risen in the firmament of Persia, that tongue deserveth every praise.

Bahá’u’lláh, The Tabernacle of Unity, p. 20

We have formerly referred to this subject in passages revealed in the Arabic tongue, in a language of exquisite beauty. God is Our witness! Whoever hath tasted the sweetness of those words will never consent to transgress the bounds which God hath fixed, neither will he turn his gaze towards any one except his Well-Beloved.

Bahá’u’lláh, Gleanings from the Writings of Bahá’u’lláh, p. 297