1 Samuel 6:9-10

9And see; if it goeth up by the way of its own border to Beth-shemesh, then he hath done us this great evil: but if not, then we shall know that it is not his hand that smote us; it was a chance that happened to us.

10And the men did so, and took two milch kine, and tied them to the cart, and shut up their calves at home;