1 Samuel 6:9-10

9But continue to watch it carefully. The cows may pull it across our border to Beth Shemesh in Israel. If that happens, we will know that the God of Israel has punished us with this great trouble. But if the cart goes somewhere else, we will know that it was not their God who did this to us. We will know that our disease happened only by chance.’

10So the Philistines did what the priests and magicians told them. They took two cows that had just given birth to calves. They tied the cows to a cart. They took away their calves and they kept them at home.