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If a male Hebrew slave was given a wife by his owner, the wife and any children by their marriage during his tenure remained the property of the slave owner. (Exodus 21:1-4) Adam Clarke comments "It was a law among the Hebrews, that if a Hebrew had children by a Canannitish woman, those children must be considered as Canaanitish only, and might be sold and bought, and serve for ever. The law here refers to such a case only."
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http://en.wikipedia.org/wiki/The_Bible_and_slavery#Israelite_slaves
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A father could sell his unmarried daughters into servitude, with the expectation that the master or his son would eventually marry her. Apparently the resulting period of servitude took the place of a dowry.
- "And if a man sells his daughter to be a female servant, she shall not go out as the male servant do. If she does not please her master, who has betrothed her to himself, then he shall let her be redeemed. He shall have no right to sell her to a foreign people, since he has dealt deceitfully with her. And if he has betrothed her to his son, he shall deal with her according to the custom of daughters. If he takes another wife, he shall not diminish her food, her clothing, and her marriage rights. And if he does not do these three for her, then she shall go out free, without paying money." (Exodus 21:7-11)
Foreigners who dwelt among the Hebrews were not to be oppressed, but loved as one of their own (Leviticus 19:33-34), and could also buy and sell Hebrew slaves. However, these could be redeemed out of slavery by close kin, for a price corresponding to the year of the jubilee. If not redeemed he was to then go free at that time. (Leviticus 25:47-55)
