Tafsir of Ash-Shu`ara' 26:172

We annihilated them with the most severe and hideous form of destruction, and that was the overturning [of the cities]. The apparent meaning is that it is a conjunction following {We saved} [in the previous verse]. Destruction is delayed relative to salvation from absolute punishment, so there is no need to claim that the meaning is "We intended his salvation," or "We decreed it," or that the meaning of {So We saved him} is "We responded to his supplication regarding his salvation." All of those are contrary to the apparent meaning.

Al-Tayyibi permitted that "then" (thumma) denotes a delay in rank.