1 Samuel 6:7

Milch kine, &c. — In respect to the ark; and for the better discovery, because such untamed heifers are apt to wander, and keep no certain and constant paths, as oxen accustomed to the yoke do, and therefore were most unlikely to keep the direct road to Israel's land. From them — Which would stir up natural affection in their dams, and cause them rather to return home, than to go to a strange country.