Tafsir of Sad 38:74

{Except Iblis} – this is a connected exception, because although he was a jinn, he was counted among the rank of the angels, described by their attributes, not standing or sitting except with them; thus, the term "angels" included him through the dominance of the category. Then, one exception was made from among them, or because there is a species among the angels that reproduces, and he was of them. Alternatively, it is a disconnected exception.

His statement—the Exalted—{he was arrogant} is, according to the first interpretation, an initiation of speech explaining the manner of his abandoning prostration, which is understood from the exception; for his abandonment could be interpreted as hesitation or contemplation, so it is confirmed that it was due to refusal and arrogance. According to the second, it is permissible for it to be connected to what precedes it, meaning: "But Iblis was arrogant and haughty."

{And he was of the disbelievers}

Meaning: He became one of them through his arrogance and haughtiness against the command of Allah—the Exalted. The omission of the fa (the letter indicating causality) is a reference to the intelligence of the listener or because the intended meaning is obvious. That arrogance against His command—the Majestic and Exalted—especially when delivered orally, necessitates disbelief is something that should not be doubted. Furthermore, this arrogance contained an element of deeming the command ugly and considering it an injustice. It is also possible that the meaning is: "And he was [already] among the disbelievers in the knowledge of Allah," because He—the Exalted—knew that he would disobey Him and that what would proceed from him would occur through his own choice, the corruption of his inner self, and his inherent disposition.