Tafsir of Saba' 34:5

"As striving to frustrate [Our will]" (That is, racing ahead, thinking they can escape Us. Qatadah said this. Ikrimah said: opposing. Ibn Zayd said: struggling to invalidate them).

A group read "mu'jizin" (striving to frustrate) with a lightened jim, while Ibn Kathir, Abu Amr, al-Jahdari, and Abu al-Summal read it with a heavy jim (stressed). Ibn al-Zubayr said: that is, discouraging those who desire faith from it, causing them to falter in their enthusiasm. It is also said: they are those who [think they can] frustrate the power of Allah—Exalted and Majestic is He—in their own estimation.

"Those" (Described with what has been mentioned, and in this there is an indication of the depth of their status in evil)

"For them" (Because of that)

"Is a punishment from a loathsome evil" (That is, from the worst and most severe of punishments; "from" here is for clarification)

"Painful" (In the nominative case, as an adjective for "punishment". Most of the seven reciters read it in the genitive case, as an adjective emphasizing "loathsome evil," based on what you have heard of its meaning. Some considered it an additional description for it, based on the view that al-rijz—as narrated from Qatadah—is punishment in a general sense. It is also permissible to consider it an adjective for "punishment," with the genitive case used due to proximity [to rijz]. The apparent meaning is that the relative pronoun [those] is the subject, and the predicate is the sentence "Those for them is a punishment." It is also permissible for it to be in the accusative case as a conjunction to the previous relative pronoun, meaning: "And He shall reward those who strove..." and the sentence "Those for them..." which follows it is a new beginning, and the one before it is parenthetical.)

In al-Bahr, it is suggested that if it is in the accusative case, the two sentences starting with "Those" might refer to the reward and punishment themselves, or they might be new beginnings, and the reward and punishment might be something other than what is explicitly contained within them, such as what is greater, like Allah the Exalted’s perpetual pleasure with the believer and His perpetual wrath against the disbeliever. Therein is the objection of how it is possible to interpret this as Allah’s pleasure and its opposite, when the text has explicitly declared first the forgiveness and honorable provision, and in opposition to it, the painful punishment, making the former the recompense.