Tafsir of Al-Hijr 15:32

(He said, "O Iblis...")

This is an initiation of speech based on a potential question from one who asks: "What did the Lord, may He be exalted, say upon his refusal?" It is said that He, glory be to Him, said:

"O Iblis, what is the matter with you?"—meaning, what is the cause for you, as is necessitated by the [coming] answer.

His saying, "that you are not among those who prostrate," means: what prevented you from being—in the state of—those who prostrate?

The use of the future tense form [in an la takuna] carries an intimation of the increased ugliness of his state. Perhaps the rebuke is not merely for his lagging behind those noble ones, but for matters narrated separately, indicating that each one of them is sufficient for the rebuke and for demonstrating the invalidity and heinousness of what he committed. The narration of the rebuke is omitted entirely in some other Surahs, contenting [the reader] with its narration in another place.

It is apparent that God’s saying of that to him was not through an intermediary; this is a lofty station, provided it is by way of exaltation and glorification, rather than insult and humiliation, as is not hidden.