What follows is my provisional translation (in other words, not official or authorized; see here for more) of a passage from a Tablet of ‘Abdu’l-Bahá to Ḥájí Níyáz of Kirmán, the original text of which has been published in Khúshih-Há’í az Kharman-i-Adab va Hunar, vol. 1, p. 67. I am grateful to Faruq Izadinia for identifying that source.
. . . The Báb, may my spirit be a sacrifice for Him, completely abrogated the rules of that tongue. He freed the language of the Arabs. Thus did all the Writings of that Exalted One, may my life be offered up for the ground His footsteps have trodden, destroy the foundation on which the rules of the Arabic language were based. The Blessed Beauty, may my soul be a ransom for His loved ones, also contravened, in the earliest of His holy Writings, the fanciful rules of that language—but in the Most Great Prison, owing to the objections raised by some of the divines, the Writings and verses were revealed in accordance with the rules of the people. In spite of this, there were occasions when, in order to prevent the language of the Arabs from falling captive once again to shackles and fetters, certain words were revealed that did not conform to these rules. Were I to elaborate, my theme would grow lengthy, and there is no time . . .
A screenshot of the original Persian text of this passage appears below.