وَلَئِن شِئْنَا لَنَذْهَبَنَّ بِٱلَّذِىٓ أَوْحَيْنَآ إِلَيْكَ
Wa la-in shiʾnā la-nadhhabanna bi'lladhī awḥaynā ilayka thumma lā tajidu laka bihi ʿalaynā wakīlā · Illā raḥmatan min rabbik, inna faḍlahu kāna ʿalayka kabīrā
"Had We willed, We would surely have taken away what We revealed to you; and then you would have found no trustee for yourself against Us in the matter. Except as a mercy from your Lord (We did not do so). His bounty towards you is truly great."
The verse comes immediately after the limit on knowledge in the eighty-fifth verse, and this placement must be recorded.
I give this as my own reading, and its support is the sequence: the preceding verse had said that the knowledge given to man is little. This verse says that what has been given can be taken back. Revelation too, that is, is a thing given — not a thing earned.
And the word wakīl occurs for the fifth time in the sūra (2, 54, 65, 68, 86). Its table was given at the fifty-fourth verse.
The usage here is different, and the difference must be recorded: in the other occurrences wakīl was named as a place of support. Here it is said that even the closest of all could find no trustee.
The form of the exception is worth recording, and this is an observation about the structure: the sentence is built like a threat, and is then turned around by a single word: illā raḥmatan.
I give this as my own reading: the verse ties the continuance of revelation not to a right but to a mercy. And the eighty-seventh verse says it once again: inna faḍlahu kāna ʿalayka kabīrā.