فَكَيفَ كانَ عَذابي وَنُذُرِ

So how were My punishment and My warnings?

EXEGESIS

As is the theme of this chapter, this verse is repeated after every story as a means of admonishment and threat for the listener.^{‎[1]Jawhar, 6/119; Kashif, 7/195.}

The purpose of this verse is also to remind the reader, and the polytheists of Mecca,^{‎[2]Tabrisi, 9/287.} to not follow the path of ʿĀd and commit the same mistakes of rejecting the truth, for it would lead to similar consequences.^{‎[3]Tibyan, 9/451.}

REVIEW OF TAFSĪR LITERATURE

Some have suggested that perhaps verse 18 was referring to their punishment in this world and this verse is referring to their punishment in the hereafter.^{‎[4]Safi, 5/102; Maraghi, 27/88.}

According to Rāzī, the reason why punishment is singular and warnings is plural is to indicate that God’s mercy outweighs His wrath. The warning He sends are a manifestation of His mercy whilst the punishment is a manifestation of His wrath.^{‎[5]Razi, 29/305.}

[1] Jawhar, 6/119; Kashif, 7/195.
[2] Tabrisi, 9/287.
[3] Tibyan, 9/451.
[4] Safi, 5/102; Maraghi, 27/88.
[5] Razi, 29/305.