Deuteronomy 23:21
19 You must not charge interest on a loan to your fellow Israelite, whether on money, food, or anything else that has been loaned with interest. 20 You may lend with interest to a foreigner, but not to your fellow Israelite; if you keep this command the Lord your God will bless you in all you undertake in the land you are about to enter to possess. 21 When you make a vow to the Lord your God you must not delay in fulfilling it, for otherwise he will surely hold you accountable as a sinner. 22 If you refrain from making a vow, it will not be sinful. 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.
Ecclesiastes 5:4
2 (5:1) Do not be rash with your mouth or hasty in your heart to bring up a matter before God, for God is in heaven and you are on earth! Therefore, let your words be few. 3 Just as dreams come when there are many cares, so the rash vow of a fool occurs when there are many words. 4 When you make a vow to God, do not delay in paying it. For God takes no pleasure in fools: Pay what you vow! 5 It is better for you not to vow than to vow and not pay it. 6 Do not let your mouth cause you to sin, and do not tell the priest, “It was a mistake!” Why make God angry at you so that he would destroy the work of your hands?
Notes and References
"... Gift-giving as initiating and maintaining a durable relation is also a recurring theme when it comes to vow making in the Hebrew Bible. Vows are made in times of crisis, as in the case of Hannah’s barrenness in 1 Samuel 1:11; but vows are also made and paid habitually as in 1 Samuel 1:21, where Elkanah and his household travel to Shiloh to offer the yearly sacrifice and to pay his vow. The relatively frequent occurrence of laws mentioning vows and the votive offering (Leviticus 7:16; 22:18–22; 27; Numbers 6:1–21; 15:8; 30; Deuteronomy 12:5; 23:18; 23:22–23) and the admonitions in Deuteronomy (23:21–22) and in Ecclesiastes (5:4) that it is better not to vow at all than it is to make a vow and break it indicate that vows were a common occurrence in everyday life ..."
Gudme, Anne Katrine "Barter Deal or Friend-Making Gift? A Reconsideration of the Conditional Vow in the Hebrew Bible" in Satlow, Michael L. (ed.) The Gift in Antiquity (pp. 189-201) Wiley-Blackwell, 2013