I maintain that [the intent of] the Torah's statement [Leviticus 19:29], "Do not defile your daughter to have her play the harlot," is that a father should not say: "Since the obligation of the Torah for a seducer or a rapist was solely that he should give the father money, I will hire my virgin daughter to someone to have relations with her for whatever price I desire, or I will allow him to have relations for her without charge. For a man has the right to forgo monetary rights to him to any person he desires." To counter such thoughts, it is written: "Do not defile your daughter."
The Torah obligates a rapist and a seducer to pay money rather than be punished by lashes when the matter happened by chance, without the knowledge of [the girl's] father, and she did not ready herself for [the relations]. For this is an extraordinary and uncommon matter.
If, however, a person leaves his virgin daughter accessible for anyone to engage in relations with her, this will cause the entire earth to be filled with sexual immorality. For [ultimately], a father will marry his daughter and a brother his sister, [for in a sexually permissive society] a [girl] may become pregnant and give birth without knowing who the child's father is.
When a person has his daughter act in this manner, she is considered to be a harlot, and both the man and the girl who engage in relations should be punished by lashes, as [Deuteronomy 23:18] states: "There shall not be a harlot."
[In such an instance,] the man is not required to pay a fine, for the Torah prescribed a fine only in the instance of seduction or rape. When a girl prepares herself [for relations] either on her initiative or on that of her father, she is a harlot. And the prohibition against harlotry applies both with regard to a virgin and a non-virgin.
For this reason our Sages stated that a girl who was reputed to have conducted herself immodestly while young is not entitled to a fine, as we have explained, for we can assume that she willingly opened herself to this experience.