Tafsir of As-Saffat 37:98

(So they plotted a scheme against him): that is, an evil plot through artifice. For when he—peace be upon him—overpowered them with his argument, they intended to punish him for that, so that their impotence would not become manifest to the common folk.

(But We made them the lowest): meaning, the most humiliated, by rendering their plot void and making his evidence as manifest as the appearance of a fire in the villages at night, serving as a sign of his high status—peace be upon him—when the Glorified One made the fire cool and a safety for him.

It is said: it means the perished ones. And it is said: it means those who will be tormented in the lowest depth of the Hellfire. The first [interpretation] is more appropriate.