Tafsir of Ash-Shu`ara' 26:185

If you ask: Did the meaning differ by including the waw (conjunction "and") here, while omitting it in the story of Thamud?

I say: When you include the waw, two meanings are intended, both of which they considered incompatible with messengership: being bewitched and being human. They believed a messenger could neither be bewitched nor be a human being. When you omit the waw, only one meaning is intended: that he is bewitched. Then, it is affirmed that he is a human being like them.

If you ask: How did the inna (the lightened form of the heavy inna) and its lam (the emphatic particle) become separated across the verb of supposition (zanna) and its second object?

I say: Their origin is to be separated across the subject (mubtada') and the predicate (khabar), as when you say: Inna Zaydan la-munṭaliqun (Indeed, Zayd is surely departing). Since the two categories—the category of kana and the category of ẓanantu—are of the same nature as the category of the subject and predicate, this was applied to both categories. Thus, it is said: In kana Zaydun la-munṭaliqan (Indeed, Zayd was surely departing) and In ẓanantuhu la-munṭaliqan (Indeed, I supposed him to be surely departing).