Tafsir of Az-Zalzala 99:3

"And man says"—meaning every individual among mankind, when they are struck by this overwhelming calamity and overtaken by this universal disaster, and when this layer of the earth is shaken and casts forth its burdens—he says this out of awe at the horrific event he is witnessing, for the mountains have been set in motion through the atmosphere and turned into scattered dust.

More than one scholar has held the view that the "man" intended here is the disbeliever who does not believe in the Resurrection. However, the more apparent meaning is the first [that it refers to all mankind], such that the believer says it out of a sense of overwhelming magnitude, and the disbeliever says it out of astonishment.