Tafsir of Al-Burooj 85:17

{Of Pharaoh and Thamud} This is a substitute (badal) for "the hosts." By "Pharaoh," he intended him and his people, as in His saying: {From Pharaoh and their chiefs} (Yunus: 83). The meaning is: You have already known the denial of those hosts toward the messengers and what befell them due to their denial.

{But those who disbelieve} From your people, are {in denial}—that is, in a state of denial and deserving of punishment. Allah is All-Knowing of their conditions and Capable over them; they cannot frustrate Him.

{And Allah is encompassing them from behind} This is a metaphor for the fact that they cannot escape Him, just as nothing can escape that which encompasses it.

The meaning of the disjunctive particle (bal - "but") is that their affair is more astonishing than the affair of those [previous nations]; for they heard the stories of what happened to them and saw the remnants of their destruction, yet they did not take heed, and they denied even more severely than those [previous nations] denied.

{But it is} That is, this [revelation] which they denied, {a Glorious Qur’an}—noble and of a high rank in the Books, in its composition, and in its inimitability. It has been recited as (Qur’anu majidin) in the genitive case, meaning: the Qur’an of a Glorious Lord.

{In a Preserved Tablet} Yahya ibn Ya‘mar recited: "In a tablet" (fi lawhin), and the lawh is the air. He means the Tablet above the seventh heaven, which contains the Tablet, {preserved} from the reach of the devils. It has also been recited as (mahfuzun) in the nominative case, as an adjective for the Qur’an.

From the Messenger of Allah (ﷺ): "Whoever recites Surah al-Buruj, Allah will give him ten good deeds for every Friday and every Day of Arafah that exists in the world."