איוב לט:כא פירוש: רש״י

They spy in the valley Heb. יחפרו, like (Deut. 1:22), “that they may spy out (ויחפרו) the land for us,” for it is the habit of the horsemen to lie in wait in the valleys and in the ravines.

and rejoices with strength The horse rejoices and goes forth toward the weapons.