Because that land was obliterated—disgraced and debased—it became a lesson, a deterrent, an admonition, and a manifest sign of Allah’s power and majesty: of His might when He avenges those who defy His command, reject His messengers, follow their lusts, and disobey their Lord; and, at the same time, a proof of His mercy toward the believing servants whom He rescues from destruction, bringing them out of darkness into light.

As the Exalted says:
“Indeed in that is a sign, yet most of them were not believers; and surely your Lord—He is the Mighty, the Merciful.” (al-Shuʿarāʾ 26:8–9)

And He says:
“So the Blast seized them at daybreak; We turned their uppermost part to the lowest and rained upon them stones of baked clay. In that are signs for those of penetrating insight; and indeed it lies upon a well-traveled road; in that, surely, is a sign for the believers.” (al-Ḥijr 15:73–77)

That is, for anyone who looks with the eye of discernment and insight: observe how Allah changed that land and its people—how, after it had been inhabited and flourishing, it was laid waste and engulfed.

Al-Tirmidhī and others relate, with an authentic chain, that the Prophet ﷺ said, “Beware the intuition of the believer, for he sees by the light of Allah,” then he recited, “In that are signs for those of penetrating insight.” (al-Ḥijr 15:75)

His words, “and indeed it lies upon a well-traveled road” (15:76), mean a clear highway still frequented to this very day, as in His saying,
“You pass by them in the morning and at night—will you not then understand?” (al-Ṣāffāt 37:137–138),
And in His saying, “We left therein a clear sign for a people who reason.” (al-ʿAnkabūt 29:35)

Likewise He says:
“We brought out from it the believers who were therein; We found in it none but a single house of Muslims, and We left therein a sign for those who fear the painful punishment.” (al-Dhāriyāt 51:35–37)

Meaning: We left it as a lesson and a reminder for anyone who fears the torment of the Hereafter, holds the Most Merciful in awe while unseen, dreads the standing before his Lord, and restrains the soul from desire—so he refrains from what Allah has forbidden and abandons sin—fearful of resembling the people of Lot, for:
“Whoever imitates a people is counted among them.”
Even if the resemblance is not complete, it is sufficient in part. One poet said:
“If you are not exactly the people of Lot themselves,
 then the people of Lot are surely not far from you.”

Thus, the intelligent, discerning servant who fears his Lord complies with what Allah has commanded him and accepts the guidance of the Messenger of Allah ﷺ: he approaches the lawful wives Allah created for him and, among female slaves, the comely maidservants, and he guards himself against following every rebellious devil—lest the threat befall him and he enter under Allah’s words, “and it is not far from the wrongdoers.” (Hūd 11:83)