1 Samuel 6:9-10

9But watch: if it goes up by the way of its own territory to 1Beth-shemesh, then He has done this great evil to us. But if not, then 2we will know that it was not His hand that struck us; it happened to us by chance.”

10Then the men did so: they took two milk cows and hitched them to the cart, and shut in their calves at home.