Halakhah sur Le Lévitique 27:2

The commandment that one who appraises a man give the value delineated in the Torah: To rule on appraisals of people; that is, one who says, "My appraisal is upon me" or "The appraisal of x is upon me," must give to the priest according to the amount that he said, and not less - as appears explicitly in Scripture about a male and female and according to the tally of [their] years - as it is stated (Leviticus 27:2), "If a man proclaims an oath of the appraisal of souls to the Lord." And the matter of appraisals is included in vows of consecration and we are therefore obligated to keep them on account of "he shall not profane his words" (Numbers 30:3), "you shall not delay" (Deuteronomy 23:22) and "he shall do like everything that comes out of his mouth" (Numbers 30:3).