Deuteronomy 23:22-24

22But if you refrain from making a vow, that would not be [counted as] sin in you.

23You 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).

24“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].