Hud: 12
"Then perhaps you would leave out some of what is revealed to you..."
They used to propose signs to him out of obstinacy, not for guidance. Had they been seeking guidance, a single sign from what he brought would have sufficed for their direction. Among their proposals was: "Why has a treasure not been sent down to him, or an angel come with him?" They did not value the Qur'an, treating it and the other clear proofs he brought with contempt.
The Messenger of Allah (ﷺ) would feel distressed that he had to present to them what they would not accept and would only mock. So, Allah stirred him and urged him to fulfill the message, disregarding their rejection, mockery, and proposals, by saying:
"Then perhaps you would leave out some of what is revealed to you" — meaning, perhaps you might refrain from presenting it to them and conveying it to them, fearing their rejection and contempt.
"And your breast is distressed by it" — by reciting it to them.
"Lest they say" — fearing they might say: "Why has a treasure not been sent down to him?" — meaning, why was what we proposed—the treasure and the angels—not sent down to him, and why was he sent what we do not want or propose?
Then He said: "You are only a warner" — meaning, you have no duty other than to warn them with what has been revealed to you and to convey what you have been commanded to convey. It is not your concern whether they reject, treat it with contempt, or make proposals.
"And Allah is, over all things, Disposer of affairs" — He preserves what they say and will do with them what must be done. So, rely upon Him, entrust your affair to Him, and proceed with conveying the revelation with a spacious heart and an expanded breast, paying no heed to their arrogance and indifferent to their foolishness and mockery.
If you ask: Why did He shift from ḍayyiq (narrow/distressed) to ḍā'iq (distressing/narrowing)?
I say: To indicate that it is a transient distress, not a permanent one, for the Messenger of Allah (ﷺ) had the most spacious breast of all people. It is like saying "Zayd is sayyid (a master) and jawād (generous)," intending established, permanent mastery and generosity. If you intend something occurring, you say sā'id (becoming a master) and jā'id (becoming generous). Similar to this is the usage of "they were a blind people" in some readings, and the verse of al-Samhari al-'Ukli:
Regarding the base person, he is fat (sāmin) in it,
While the noble people are showing signs of emaciation (bād).
"Or do they say, 'He invented it'? Say, 'Then bring ten surahs like it that have been invented, and call upon [for assistance] whomever you can besides Allah, if you should be truthful.'"