Tafsir of Al-Qasas 28:66

The origin of this expression is "they were blind to the tidings," meaning they were not guided to them. It contains a metaphorical derivative (isti'arah tasrihiyyah tabaiyyah), wherein "blindness" is used metaphorically for the lack of guidance. Then, it is inverted for the sake of hyperbole, so that the "tidings" are made unable to be guided to them. The word "blindness" (al-'ama) is endowed with the meaning of concealment (al-khafa'), which is why it is used with the preposition 'ala (on/to); were it not for this, it would have been used with 'an (from). It does not relate to the tidings because they are heard, not seen.

This inversion indicates that whatever is present in the mind flows into it and reaches it from the outside—either directly or through the recollection of an image derived from it by its external signs. If the mind fails to reach the outside, such as when the path between them is obstructed by blindness or the like, it becomes impossible for the mind to present or retrieve [information]. By making the tidings reaching them from the outside "blind" and unable to find their way, it demonstrates by greater force that they themselves are blind and incapable of being guided; for their guidance depends upon those tidings. If the tidings themselves cannot find their way, then what of those who are meant to be guided by them? This is how it has been argued; reflect upon it.

It is also permitted that the speech contains a metaphorical imagery (isti'arah makniyyah takhyiliyyah), meaning: the tidings became like blindness upon them, unable to reach them. The "tidings" refer either to that which was demanded of them—namely, the answers they were asked to give the Messengers (peace be upon them)—or something that encompasses that and all that is possible to answer with. If the Messengers (peace be upon them) falter in answering such questions in that horrific station and delegate the knowledge to the All-Knower of the Unseen, despite their immunity from the consequences of what is asked, what then is your assumption regarding those misguided nations?

Al-A'mash, Janah ibn Hubaysh, and Abu Zur'ah ibn 'Amr ibn Jarir read it as fu'miyat (with a damma on the 'ayn and a shadda on the mim).

Meaning: they do not ask one another, due to excessive shock, or due to the knowledge that all are equal in ignorance. The fa' (so/then) is either for detailing or for deriving consequences, as the cause of the blindness is the excessive shock. Talha read it as la yusa'alun (by assimilating the ta' into the sin).