Kiddushin 19A

מי שאני?

is the matter different? In both cases she is fully released from her father’s authority by Torah law, and therefore he should not be able to sell her again afterward.

ולרב נחמן בר יצחק דאמר: אפילו לרבי יוסי ברבי יהודה מעות הראשונות לקידושין ניתנו, במאי מוקים לה? מוקים לה כרבי אליעזר דאמר: לשפחות אחר שפחות הוא דלא מצי מזבין לה, אבל לשפחות אחר אישות ⁠– מצי מזבין לה.

The Talmud asks: And according to the explanation of Rav Naḥman bar Yitzḥak, who says that even according to R' Yosei, son of R' Yehuda, the original money of the sale of the female slave was given for the purpose of betrothal, in accordance with whose opinion does he establish the baraita that permits a father to sell his widowed daughter? After giving her in marriage a father may no longer sell his daughter into slavery. The Talmud explains: He establishes it in accordance with the opinion of R' Eliezer, who says: It is for slavery after slavery that he is not able to sell her, but he is able to sell her into slavery after marriage.

בעי ריש לקיש: מהו שמייעד אדם לבנו קטן? ״בנו״ אמר רחמנא, בנו כל דהו, או דילמא בנו דומיא דידיה, מה הוא גדול ⁠– אף בנו גדול?

§ Reish Lakish raises a dilemma: With regard to the possibility that a person can designate a Hebrew female slave for his minor son, what is the halakha? The Talmud clarifies the sides of this dilemma. Does one learn from the verse: “And if he designates her for his son” (Exodus 21:9), that God states that this applies to any son, even if he is too young to be married? Or perhaps it means his son who is similar to him: Just as he is an adult man, so too, his son must be an adult man.

אמר רבי זירא: תא שמע: ״איש״⁠ – פרט לקטן. ״אשר ינאף את אשת איש״⁠ – פרט לאשת קטן. ואי אמרת מייעד, אם כן מצינו אישות לקטן.

R' Zeira said: Come and hear a solution to this dilemma from the verse: “And the man who commits adultery with the wife of another man, even he that commits adultery with his neighbor’s wife, both the adulterer and the adulteress should surely be put to death” (Leviticus 20:10). The rabbis expounded that the term “man” serves to exclude a minor who commits adultery. The phrase “who commits adultery with the wife of another man” serves to exclude the wife of a minor, as the marriage of a minor is invalid. And if you say that a father can designate a wife for his minor son, and designation effects betrothal or marriage, we find that there is marriage for a minor.