Make a new cart; as David did for the same use, 2 Samuel 6:3, in reverence to the ark. On which there hath come no yoke; partly in respect to the ark, and partly for the better discovery, because such untamed heifers are wanton, and 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. Bring their calves home 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.
Related Commentaries of 1 Samuel 6:7
1 Samuel 6:7
7 Now therefore make a new cart, and take two milch kine, on which there hath come no yoke, and tie the kine to the cart, and bring their calves home from them: