Tafsir of Fussilat 41:15

"As for 'Ad, they were arrogant in the land" — This is the beginning of a detailed account of the crimes and punishments pertaining to each of the two groups. Because this detail follows a summary, it is connected with the fa of causality. The story of 'Ad is mentioned first because it is older in time. That is, the people of 'Ad behaved with haughtiness in the land—a land wherein one should not be haughty toward its people—"without right," meaning: without any justification for such haughtiness. It has been said: they were haughty regarding the compliance with the command of Allah, the Exalted and Majestic, and the acceptance of what the messengers brought to them.

"And they said," in their delusion regarding their own strength: "Who is mightier than us in strength?" That is: there is no one mightier than us in strength. The interrogation here is one of denial, serving as an explanation for their sense of greatness and their response to the messengers regarding the punishment they were warned about. They were people of tall stature and immense creation; it reached such a degree of strength that a man would pull a boulder from a mountain and lift it with his hand.

"Do they not see" — meaning: have they been heedless and failed to look, or have they not known with a clear knowledge that resembles visual observation and sight — "that Allah, who created them, is mightier than them in strength?" [He is mightier] in power; for He, the Exalted, is Powerful in His Essence, capable of what is infinite, strong over that which others are incapable of—Exalted and Majestic is He—and He is the Bestower of strength and power upon every strong and capable being. In this, there is an intimation that the punishment with which the messengers threatened them was not from the messengers themselves, based on any strength they possessed, but rather it was from Allah the Exalted, the Creator of strengths and powers. They know that He, the Exalted, is mightier in strength than they are. Strength is interpreted here as power, as it is one of its meanings, as indicated by the words of al-Raghib.

Some have claimed that "strength" is an accidental attribute from which Allah is exalted; however, it necessitates power, and therefore it is expressed as such in harmony [with the verse]. He brought "created them" into the relative clause instead of "created the heavens and the earth" because of their claim of excessive strength, and therein lies a form of mockery toward them.

"And they were rejecting Our signs" — meaning: they denied them while knowing their truthfulness. This is a conjunction to "they were arrogant" or "they said." Thus, the sentence "Do they not see," along with what is conjoined to it, is a parenthetical clause. It is also permissible that it alone is the parenthetical clause, with the waw being an introductory particle of digression rather than a conjunction.