Deuteronomy 23:23-25

You shall be careful to do what has passed your lips, for you have voluntarily vowed to the LORD your God what you have promised with your mouth. “If you go into your neighbor’s vineyard, you may eat your fill of grapes, as many as you wish, but you shall not put any in your bag. If you go into your neighbor’s standing grain, you may pluck the ears with your hand, but you shall not put a sickle to your neighbor’s standing grain.