Tafsir of Al-Qalam 68:33

This is a nominal sentence composed of a predicate placed before the subject to signify restriction (qaṣr). The definite article (al) is for referring to something previously mentioned; that is, such is the punishment—like that with which We tested the people of Makkah through severe drought, and [like that of] the companions of the garden—of what has been narrated of worldly punishment.

It is said that this discourse is presented as a warning to them. It is as if, when He, Glory be to Him, forbade him [the Prophet] from obeying the disbelievers—especially their leaders—He, the Almighty and Majestic, mentioned that their rebellion stemmed from the wealth and children they possessed. He followed this by stating that if these two [wealth and children] do not lead to gratitude toward the Bestower, the condition of their possessor will inevitably reach the state of the companions of the garden. Embedded within this is the fact that if the intention is corrupt and one turns away from the poor, leading them to what was mentioned, then opposing the Truth (the Almighty) by antagonizing the one who is the most noble of His creation and the most honored of existing beings, and severing ties of kinship, is more certain to lead the people of Makkah to ruin.

That is, it is more immense and more severe—a warning against stubbornness in a more eloquent manner.

This is a condemnation of their heedlessness. That is, if they were people of knowledge, they would have known that it is greater, and they would have taken their precautions against it.