Deuteronomy 23:21-23 - Keeping Vows
21 When you shall vow a vow to Jehovah your God, you shall not wait to pay it, for Jehovah your God will surely require it of you, and it would be sin in you. 22 But if you shall cease to vow, it shall be no sin in you. 23 That which has gone out of your lips you shall keep and perform, even a free-will offering, according as you have vowed to Jehovah your God, which you have promised with your mouth.