John Trapp on Job 39:21

Verſe 21. He paweth in the valley] —Cavatque Tellurem, & ſolido graviter ſonat ungula cornu.Virg. Georg. l. 3 Such is the impatiency of his ſpirit, that he champs his bit, and ſtamps with his feet;Quadrupedante putrem ſonitu quatit ungula Campum. Virg. he pricks up his eares, and growes white with foame, and can hardly be held in till the enemy come, but would fain be in the battle; whither when he comes, he runs upon the Pikes, and undauntedly caſts himſelf and his rider among the enemies ſquadrons: Quod ſummè mirum eſt, ſaith Mercer. which is a wonderful thing indeed: and it is no leſs wonderfully ſet forth by a moſt lively and lightſome hypotypoſis, giving us to ſee, as it were, the horſes ruſhing into the battle, and to hear him ſnoaring, and ſnorting with diſdain and deſpight, bringing every where horror and diſorder.