Job 37:2

Hear — It is probable that while Elihu was speaking it thundered, and that tempest was begun, wherewith God ushered in his speech. And this might occasion his return to that subject of which he had discoursed before. Voice — The thunder is called God's voice. Because by it God speaks to the children of men, to fear before him. Mouth — That is produced by God's word or command, which is often signified by his mouth.