Deuteronomy 23:22-26

However, if you refrain from making vows, it will not be a sin for you.

You shall be careful and perform what goes out of your lips, since in fact you have vowed a voluntary offering to the Lord your God, whatever you have promised.

“When you enter your neighbor’s vineyard, you may eat grapes until you are satisfied; but you are not to put any in your basket.

“When you enter your neighbor’s standing grain, you may pluck the heads of grain with your hand, but you are not to use a sickle on your neighbor’s standing grain.