What follows is my provisional translation (in other words, not official or authorized; see here for more) of a passage from a Tablet of ʻAbduʼl-Bahá, the original text of which is published in Máʼidiy-i-Ásmání, vol. 2, pp. 34–35.
The word jinn in the Qurʼán referreth to those whose belief and rejection alike are concealed. The jinn is a hidden being, wherefore hath it been said: “They behold you from a place where ye cannot behold them.”* In other words, they are apprised of your faith and certitude, but the measure of their own faith and certitude is concealed to you. A jinn is he in whom lie hid the light of faith or the fire of rebellion.
* Likely a reference to Qurʼán 7:27.
A typescript of the complete Persian and Arabic text of this passage appears below. All Arabic vocalization is mine.