Tafsir of Al-Mutaffifeen 83:34

"So today, those who believed" — meaning those known from among the poor [who were mocked] by the disbelievers, or [alternatively] it may be interpreted as the ones known from both sides. It is also permissible to apply it generally to both groups.

"...laugh," at the time they see them [the disbelievers] disgraced and shackled, having been overwhelmed by various forms of humiliation and abasement after their [former] glory and arrogance, and afflicted with various types of torment after their [former] luxury and comfort.

The adverbial phrase and the prepositional phrase ("So today") are linked to the verb "laugh." It has been said that the placement of the prepositional phrase before the verb serves the purpose of restriction (qasr), to realize the perfect opposition [to the state of the world]; meaning: "And today, it is they who laugh at the disbelievers, not the disbelievers who laugh at them, as they used to do in the worldly life."

And [concerning] His saying, the Exalted...