Deuteronomy 23:22-25

23:22 If you refrain from making a vow, it will not be sinful. 23:23 Whatever you vow, you must be careful to do what you have promised, such as what you have vowed to the Lord your God as a freewill offering. 23:24 When you enter the vineyard of your neighbor you may eat as many grapes as you please, but you must not take away any in a container. 23:25 When you go into the ripe grain fields of your neighbor you may pluck off the kernels with your hand, but you must not use a sickle on your neighbor’s ripe grain.