21:7-9 A female slave was treated differently from a male, possibly because it was understood that she was sold to become a concubine. For such a woman to be released after seven years would not be just. She would either have to return to her father (who clearly did not want her, having previously sold her), marry (an unlikely prospect for a former concubine), or become a prostitute. Thus, it was best for her to remain in the home of her master. Presumably, if a man bought a girl to be his son’s wife (21:9), it was understood that the purchase price was not actually buying her but was the equivalent of a bride-price. Typically, a young man wishing to marry a girl had to give her father a gift of some sort, either money or a gift in kind (see 22:16; Gen 24:53). A woman for whom a bride-price had been paid was not a slave.