Tafsir of Fussilat 41:23

"And that" is a pointer referring to their assumption mentioned within His saying, the Almighty: "which you assumed." The element of distance contained within it serves to signal the extreme remoteness of its status in terms of evil and foulness. It is the subject (mubtada').

His saying, the Almighty: "your assumption which you assumed concerning your Lord," is in apposition (badal) to it. His saying, the Almighty: "has brought you to ruin" (i.e., has destroyed you), is its predicate (khabar).

It has been permitted that "your assumption" be the predicate, and "has brought you to ruin" be a subsequent predicate. Abu Hayyan rejected this, arguing that "that" points to their aforementioned assumption, making the implication: "Your assumption concerning your Lord [is] that He does not know your assumption concerning your Lord." Thus, what is gained from the predicate is the same as what is gained from the subject, which is impermissible—similar to the saying: "The master of the slave-girl is her owner," which grammarians have forbidden.

It was answered that the necessity mentioned does not follow, because it is permissible to make the reference point to the matter being of great repulsiveness, whereby the concept differs according to the label, and predication becomes valid, as in: "This is Zayd." Even if that were granted, the union is similar to the saying: "I am Abu al-Najm, and my poetry is my poetry," which signifies perfection in beauty, as in this example, or in ugliness, as in the aforementioned sentence.

It was also said that what is intended by it is astonishment and mockery, and the predicate may be intended for something other than the benefit of the predicate itself or its necessary implication. Some have chosen as an answer that which Ibn Hisham pointed to in Sharh Banat Su'ad, where he elaborated that the benefit, just as it is obtained from the predicate, is also obtained from its attribute and qualifier, such as the circumstantial qualifier (hal). It was permitted for the sentence "has brought you to ruin" to be a circumstantial qualifier, assuming the presence of "qad" or without it. The relative pronoun (al-mawsul) in all these aspects is an attribute of "your assumption." It was also said that the three are predicates, so do not be heedless.

"So you became..."—due to that evil assumption which destroyed you—"...among the losers."

(This is because what was given to them in terms of limbs—for the attainment of happiness in this world and the Hereafter, as by them is their livelihood in this world, and their perception, through which they are guided to certainty and the knowledge of the Lord of the worlds, which leads to otherworldly happiness—became a cause of misery in both abodes, as it led them to deny the favors of the Provider, disbelief in the Creator, immersion in heedlessness, committing acts of disobedience, and following desires.)