Tafsir of Sad 38:67

That is: This which I have informed you of—my being a messenger and a warner, and that Allah is One, having no partner—is a great news. None would turn away from the like of it except one who is heedless, in a state of extreme heedlessness.

Then, he argued for the validity of his prophethood by stating that what he informs of regarding the Highest Assembly and their dispute is a matter he had absolutely no knowledge of. He then came to know it without following the path people usually take to acquire knowledge—which is learning from scholars or reading books. Thus, it is known that this was only attained through revelation from Allah.

That is: "It is not for anything except that I am a warner." The lam (preposition) was omitted, and the verb became accusative due to the verb acting directly upon it. It is also permissible for it to be nominative, meaning: "Nothing is revealed to me except this," which is that I warn and convey, and I do not exceed that. That is: I am not commanded except with this matter alone, and nothing else is upon me. It has been recited as innama (with a kasra) as a quotation, meaning: "Except this statement," which is that I say to you: "I am only a clear warner," and I do not claim anything else.

It has been said: The "great news" is the story of Adam (peace be upon him) and the informing of it without having heard it from anyone. Ibn Abbas said: It is the Quran. Al-Hasan said: It is the Day of Resurrection.

If you ask: To what does {when they were disputing} relate? I say: To an omitted element, for the meaning is: I had no knowledge of the speech of the Highest Assembly at the time they were disputing. {When He said} is a substitute for {when they were disputing}.

If you ask: What is meant by the "Highest Assembly"? I say: The subjects of the story: the angels, Adam, and Iblis, for they were in the heavens and the dialogue took place among them.

If you ask: What dialogue took place among them? It was only between Allah (Exalted is He) and them, for Allah (Glorified and Exalted is He) is the One who said to them, and they said to Him. So you are between two options: either you say the Highest Assembly is them, and the dialogue was among them (though there was no dialogue among them), or you say the dialogue was between Allah and them, and you have included Him in the "Highest Assembly."

I say: The dialogue of Allah (Exalted is He) was through the mediation of an angel. Thus, the one speaking in reality was the intermediary angel, so it is correct that the dialogue was between the angels, Adam, and Iblis, and they are the Highest Assembly. The meaning of "disputing" is the dialogue mentioned previously.