Adam Clarke on Job 5:21

Thou shalt be hid from the scourge of the tongue - The Targum refers this to the incantations of Balaam: "From injury by the tongue of Balaam thou shalt be hidden in the clouds; and thou shalt not fear from the blasting of the Midianites, when it shall come." Perhaps no evil is more dreadful than the scourge of the tongue: evil-speaking, detraction, backbiting, calumny, slander, tale-bearing, whispering, and scandalizing, are some of the terms which we use when endeavoring to express the baleful influence and effects of that member, which is a world of fire, kindled from the nethermost hell. The Scripture abounds with invectives and execrations against it. See Psa 31:20; Psa 52:2-4; Pro 12:18; Pro 14:3; Jam 3:1-8.

Neither shalt thou be afraid - "Thou shouldst have such strong confidence in God, that even in the presence of destruction thou shouldst not fear death," the God of life and power being with thee.