Tafsir of Ar-Rum 30:9

{Have they not traveled} An affirmation of their traveling through the land and their observation of the ruins of those destroyed, such as ‘Ād, Thamūd, and other defiant nations.

{Then He began to describe their conditions to them, and that they {were stronger than them in power, and they plowed the earth}} They cultivated it. God Almighty said: "Not trained to plow the earth" (Al-Baqarah: 71). Plow-oxen are called al-muthīra (the plowers). It is said that the ox (thawr) is named for its plowing (ithāra) of the earth, and the cow (baqara) because it splits (tabqaruha) it.

{And they built it up} Meaning those destroyed ones built it up {more than they have built it up}—referring to the building up done by the people of Mecca. The people of Mecca are the people of a valley without cultivation; they have no plowing of the earth at all, nor any building of it whatsoever. This is nothing but mockery of them and their weak state in worldly matters, for most of what the people of the world rely upon and boast about is the matter of agriculture. They (the Meccans) are also weak in power.

{So His saying: {They were stronger than them in power}} Meaning ‘Ād, Thamūd, and their likes are of this category. It is like His saying: "Have they not seen that Allah, who created them, is stronger than them in power?" (Fuṣṣilat: 15), though this (the current verse) is more eloquent, as He is the Creator of power and ability.

His destruction of them was not an injustice to them, for His state is incompatible with injustice; rather, they wronged themselves when they committed that which necessitated their destruction.

{Then the end of those who did evil was the worst [consequence] because they denied the signs of Allah and used to mock them.}