Vows were not commanded by the Law of YeHoVaH, but were made by individuals who wanted to do something over and beyond what was required by YeHoVaH in exchange for something. Typically, vows were made to dedicate or devote someone or something of value to the service of YeHoVaH.
In this final chapter of Leviticus, YeHoVaH gives Instructions for the vow being made, the value of the person or the thing that is vowed, and the process for redeeming that which had been vowed.
In preparation for the study of Vows, Values and Redemption, please read Leviticus 27:1-34.