Az-Zumar: 38
"And if you ask them, 'Who...'"
It is recited: kāshifāt ḍurrihi (removers of His harm) and mumsikāt raḥmatihi (withholders of His mercy), both with tanwīn (nunation) according to the original grammatical rule, and with iḍāfa (genitive construction) for the sake of brevity.
If you ask: Why did he pose the question regarding himself rather than them?
I say: Because they threatened him with the disgrace and madness of the idols. He was commanded to first make them acknowledge that the Creator of the world is Allah alone. Then, after this acknowledgment, he says to them: "If the Creator of the world—whom you have acknowledged—wills for me harm, such as illness, poverty, or other calamities, or wills for me His mercy, such as health, wealth, or the like, are these [idols] you have threatened me with capable of removing His harm or withholding His mercy?"
Once he has silenced them completely, leaving them unable to utter a single word, he says: "Sufficient for me is Allah"—sufficient against the disgrace of your idols—"upon Him rely the [true] relyers." There is mockery in this. It is narrated that the Prophet (peace be upon him) asked them this, and they remained silent, so the verse "Say: Sufficient for me is Allah" was revealed.
If you ask: Why were the feminine forms kāshifāt (removers) and mumsikāt (withholders) used after the Almighty’s saying: "And they threaten you with those other than Him [masculine plural]?"
I say: He used the feminine because they were indeed female—namely, al-Lāt, al-‘Uzzā, and Manāt. Allah the Almighty says: "Have you considered al-Lāt and al-‘Uzzā? And Manāt, the third, the other one? Is the male for you and for Him the female?" (An-Najm: 19-21). He did this to weaken and incapacitate them further, beyond the incapacity already demanded of them regarding the removal of harm and the withholding of mercy. This is because femininity is associated with softness and weakness, just as masculinity is associated with strength and firmness. It is as if He said: "These females—al-Lāt, al-‘Uzzā, and Manāt—are even weaker and more incapable than what you claim for them." There is mockery in this as well.
"Say, 'O my people, work according to your position; indeed, I am working. You will come to know who will get a punishment that will disgrace him and upon whom will descend an enduring punishment.'"