Rashi (on Pasuk 10) and Seforno: The Torah is referring to what they did by the plague of Dever, ¹ and what the Pasuk means is that following the reaction of the those who feared Him there, and that those who didn't fear Him suffered the consequences, He instructed the people now to gather in their animals and slaves now or they would suffer the same fate.

Targum Yonasan: Because those who feared Hashem refers predominantly to Iyov, and those who didn't, to Bil'am, ² two of Pharaoh's three counselors, who played major role in Pharaoh's treatment of Yisrael. ³