Tafsir of Al-Qalam 68:19

{طائف}: That is, an encompassing affliction; it is an adjective for a deleted noun. Qatadah’s statement that ta'if means "punishment" is an explanation of the resulting meaning, and Ibn Abbas’s statement that it means "a matter" is similar. Al-Farra’ specified the ta'if as a matter that arrives at night. According to Ibn Jurayj, it was a tongue of fire that emerged from the valley of their garden. It is also said that the ta'if was Gabriel (peace be upon him), who uprooted it and circled it around the city, then placed it near Makkah where the city of Ta'if is today; this is why it was named "Ta'if," and there is no town in the land of Hijaz that possesses water, trees, and grapes other than it. In my view, this is not sound, just like the claim that the city of Ta'if mentioned was in the Levant, and God the Exalted moved it to the Hijaz due to the supplication of Abraham (peace be upon him). The same applies to the claim that it floated on the water during the Flood. If all of this were taken at its literal face value, it would be a tall tale that cannot be considered anything but a tall tale. Al-Nakha'i recited it as tayf.

{من ربك}: (From your Lord): Initiated from His side, the Exalted and Majestic.

{وهم نائمون}: (While they were sleeping): This is in the position of a state (hal). The intent is that it came to it at night, as was narrated from Qatadah. It is also said the intent is "while they were heedless," in a state of complete heedlessness regarding what the decrees had ordained. The first is more apparent from the perspective of the context and the connection.