1 Samuel 6:6-10

Why then do you harden your hearts as the Egyptians and Pharaoh hardened their hearts? When He had severely dealt with them, did they not let the people go, and they left?

Now then, take and prepare a new cart and two milk cows on which there has never been a yoke; and hitch the cows to the cart and take their calves back home, away from them.

Then take the ark of the Lord and place it on the cart; and put the articles of gold which you return to Him as a guilt offering in a saddlebag by its side. Then send it away that it may go.

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

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