Leviticus 7:16
16 But bif the sacrifice of his offering is a vow offering or a freewill offering, it shall be eaten on the day that he offers his sacrifice, and on the next day what remains of it shall be eaten.
Leviticus 22:23
23 You may present a bull or a lamb that has a part dtoo long or too short for a freewill offering, but for a vow offering it cannot be accepted.
Deuteronomy 23:23
23 You shall be careful to do what has passed your lips, for you have voluntarily vowed to the Lord your God what you have promised with your mouth.