Tafsir of Sad 38:86

{...any reward for it} The pronoun refers to the Qur’an or the Revelation.

{And I am not of the pretenders} Meaning: I am not among those who feign or adorn themselves with what they do not possess. You have never known me to be a pretender, nor one who claims what I do not have, such that I would fabricate prophethood or invent the Qur’an.

{It is but a reminder} From Allah.

{...to the worlds} To the Jinn and Mankind. It was revealed to me, and I am merely conveying it.

From the Messenger of Allah (ﷺ): "The pretender has three signs: he disputes with those above him, he attempts what he cannot attain, and he speaks of what he does not know."

{And you will surely know its information} Meaning: What will come to you at the time of death, or on the Day of Resurrection, or upon the emergence and spread of Islam—regarding the truthfulness of its report, and that it is the Truth and the Reality. In this, there is a threat.

From the Messenger of Allah (ﷺ): "Whoever recites Surah Sad, he shall have ten good deeds for the weight of every mountain that Allah subjected to David, and it will protect him from persisting in any sin, whether small or great."