Leviticus 27:15
And if he that sanctified it will redeem his house, then he shall add the fifth part of the money of thy estimation unto it, and it shall be his. And if he that sanctified it will redeem his house, then he shall add the fifth part of the money of thy estimation unto it, and it shall be his.
The verse belongs to the laws for valuing and redeeming things sanctified to the Lord, including a person's property such as a house. It is part of the law for sanctifying a man's substance to the Lord, governing how what has been dedicated is estimated and how it may be redeemed or exchanged. A person who had dedicated a house could redeem it by paying its assessed estimation plus one-fifth of its value, after which the house is or remains his. The one who sanctified it may thus reclaim and retain it by paying its appraised value with the fifth added.
The requirement of an added amount also applies when what was sanctified is exchanged, so it cannot simply be taken back without giving an equivalent. The added fifth completes the vow and shows that what was consecrated is sacred and cannot be turned to ordinary use without robbing God. What is sanctified is the Lord's, like the tithe, bearing His image and ownership. Civil government therefore has no right to exact, modify, direct, or lay any claim upon worship or the tithe.
Devotion under this chapter means something set apart, separated, and devoted. It can denote absolute, irrevocable, and entire separation of a person from the communion of the faithful, from the number of the living, or from the privileges of society. It can also denote the devoting of any man, animal, city, or thing to be extirpated, destroyed, consumed, and as it were annihilated. Related law allowed a household member devoted by a special vow to be redeemed according to the priest's valuation, since people were not accepted as burnt offerings. Thus Jephthah's daughter was devoted to the Lord's service and remained in lifelong virginity rather than being sacrificed.