Tafsir of Ash-Shu`ara' 26:188

{My Lord is most knowing of what you do}

He means: Allah is most knowing of your deeds and of the punishment you deserve for them. If He wills to punish you by dropping fragments from the sky, He does so; and if He wills another punishment, the judgment and the will belong to Him.

{But they denied him, so the punishment of the day of the overshadowing cloud seized them. Indeed, it was the punishment of a terrible day. Indeed in that is a sign, but most of them were not to be believers. And indeed, your Lord - He is the Exalted in Might, the Merciful.}