He paws in the valley and rejoices in his strength; he charges into battle.
God, having displayed his own power in those creatures that are strong and despise man, here shows it in one scarcely inferior to any of them in strength, and yet very tame and serviceable to man, and that is the horse, especially the horse that is prepared against the day of battle and is serviceable to man at a time when he has more than ordinary occasion for his service.
Commenting on Job 39:19-25
He paweth in the valley,.... Where armies are usually pitched and set in battle army, and especially the cavalry, for which the valley is most convenient; and here the horse is impatient of engaging, cannot stand still, but rises up with his fore feet and paws and prances, and, as the word signifies, digs the earth and makes it hollow, by a continual striking upon...
valley--where the battle is joined. goeth on--goeth forth (Num 1:3; Num 21:23).