Exodus 21:8

If she hath not found favour before her master who bought her, then her father may redeem her; but to a foreigner he shall not have power to sell her; for as a vessel of her Lord he hath power over her.

L’AM NOCHRI’ HE SHALL HAVE NO POWER TO SELL HER. “Neither her master nor her father has the right to sell her to another [Hebrew man]. [literally: “unto a foreign people”] as signifying “unto a strange man,” i.e., to another Israelite. Thus the verse is stating that neither the father nor the master has a right to resell her. Ramban will question this interpretation. Seeing he hath dealt deceitfully with her — if he [i.e. the master] intends to act deceitfully towards her and not to fulfill the commandment of designating her as his wife [or his son’s]. So also did her father act deceitfully towards her, by selling her to this master.” Thus far Rashi’s language. And if so, l’am nochri would be like l’ish nochri (to a strange man), but we find in all Scripture no parallel to such a usage [that am (people) should be understood in the sense of “man”]. Perhaps the letter lamed in the word l’am draws along with it a similar letter in the next word, thus making it: ‘l’am l’nochri’ he shall have no power to sell her, and the explanation thereof would be similar to the verse, Thou gavest him to be food ‘l’am l’tziyim’ (to the folk inhabiting the wilderness) where the second word l’tziyim explains: who is the folk? — the men who inhabit the wilderness; so here too He says, he shall have no power to sell her ‘l’am’, and He explains: who is l’am? — l’nochri, that is to say, to any stranger from the whole people [i.e., to another Israelite]. The term nochri here will then be similar in usage to the expressions: and thy labors in the house of a ‘nochri’ (stranger), which means in the house of another man; even from the ‘nochriyah’ (the strange woman) that maketh smooth her words,, 2:16. meaning the woman who is not his wife. All this I have written in order to uphold the words of the Sages who say that a man is not permitted to sell his daughter twice into the status of a handmaid, thus holding to the explanation: since he has once dealt deceitfully with her [by selling her to such a status of a handmaid], he has no more the right to sell her.
But I have seen in the Mechilta: “‘L’am nochri’ he shall have no power to sell her, — this is a warning to the court that he [i.e., the father] should not sell her to an alien [i.e., a non-Israelite].” It would thus appear from their language that this verse is not meant as an admonition against the father …

אם רעה בעיני אדוניה, and as a result he does not want to keep the implied agreement to marry her, she will not leave his employ in the manner her male counterparts would leave, but, seeing that he committed a breach of trust by not finalising the deal and marrying her (violating what the prophet Maleachi 2,14 called “the Lord is a witness between you and the wife of your youth with whom you have broken faith, although she is your partner and covenanted spouse,”) והפדה, the master has to assist her by releasing her prematurely, by allowing her to compensate the employer for unexpired years of service.

אם רעה בעיני אדוניה, even though the normal procedure is what we outlined in verse seven, her “master” does not have to marry her if he finds her incompatible, as otherwise he would eventually come to hate her. However, in such a situation the father and the master have to cooperate in releasing her from her obligation as servant.

לעם נכרי לא ימשול למכרה בבגדו בה, the father of the girl in question who had already betrayed her by “selling” her initially. We know that even Lavan’s daughters were angry at what they considered their father having done when he “sold” them into marriage. (compare Genesis 31,15) The Torah describes here the negative impression it makes on any of his peers when he observes a Jewish father selling his daughter’s services for something other than marriage. Once an employer/prospective husband, has done this no other Jewish father is allowed to sell his daughter to such a man. [the word נכרי does not refer to a non Jew, but to a Jew who acted contrary to Jewish mores. Ed.]

והפדה, “he must help her to obtain her freedom;” the unusual phrasing means that he must do more than the law requires to give her freedom, i.e. enable her to avoid having to become someone else’s “slave” due to her being penniless. Rashi explains our verse as follows: if the servant girl had been sold for six years service, for say 600 dollars, and she had only worked for two years, she must give him 400 dollars upon her going free. If you were to ask what did her master loose in that scenario, seeing that he had received the correct percentage of the work performed? The answer is that the girl’s services becoming worth more every year she grew closer to adulthood, the master had paid her for work performed while she was too young to be worth what he had paid for. In other words, the master did sustain a financial loss by her early release.