Deuteronomy 23:23-25

You shall be careful to perform what goes out from your lips, just as you have voluntarily vowed to the LORD your God, what you have promised. “When you enter your neighbor’s vineyard, then you may eat grapes until you are fully satisfied, but you shall not put any in your basket. “When you enter your neighbor’s standing grain, then you may pluck the heads with your hand, but you shall not wield a sickle in your neighbor’s standing grain.