Deuteronomy 23:23-25

You shall be careful to perform that [vow] which passes your lips, just as you have made a voluntary vow to the LORD your God, just as you have promised with your own words (mouth). “When you enter your neighbor’s vineyard, you may eat your fill of grapes, as many as you please, but you shall not put any in your basket [to take with you]. “When you come into the standing grain of your neighbor, you may pluck the ears of grain with your hand, but you shall not wield a sickle in your neighbor’s standing grain [to harvest it].