(Al-Addariyath) 51 : 37
وَتَرَكْنَا فِيهَا آيَةً لِلَّذِينَ يَخَافُونَ الْعَذَابَ الْأَلِيمَ
And We left therein a sign for those who fear painful punishment.
The Dead Sea is a sign left behind being a sign for the coming generations. See explanation 7: 84; 15: 75; 53: 53-54.