Deuteronomy 23:21-23

21“1When you make a vow to the Lord your God, you shall not delay to pay it, for the Lord your God will certainly require it of you, and it will be a sin 2for you. 22However, if you refrain from making vows, it will not be a sin 3for you. 23You shall be careful and perform what goes out of your lips, since in fact you have vowed a 4voluntary offering to the Lord your God, whatever you have 5promised.