Tafsir of Hud 11:58

{And those who believed with him} It is said: They were four thousand.

If you ask: What is the meaning of repeating the [mention of] salvation? I say: He first mentioned that when He destroyed their enemy, He saved them. Then He said: {And We saved them from a harsh punishment}, meaning: That salvation was from a harsh punishment. This is because Allah, the Mighty and Majestic, sent upon them the samum (a scorching wind), which would enter their nostrils and exit through their posteriors, severing them limb by limb.

It is also said: By the second [mention of] salvation, He meant salvation from the punishment of the Hereafter, and there is no punishment harsher or more severe than that.

His saying: {By a mercy from Us} means: By reason of the faith which We bestowed upon them by granting them the success to attain it.

{And that is ‘Ad; they rejected the signs of their Lord, disobeyed His messengers, and followed the command of every obstinate tyrant. And they were followed in this world by a curse, and [likewise] on the Day of Resurrection. Unquestionably, ‘Ad denied their Lord. Unquestionably, away with ‘Ad, the people of Hud.}