Slavery is the condition of bondage or ownership of persons.
Slavery is implicitly condoned in the old testament in several instances.
Examples: (Leviticus 25:44-46) "44 As for your slave man and your slave girl who become yours from the nations that are round about YOU people, from them YOU may buy a slave man and a slave girl. 45 And also from the sons of the settlers who are residing as aliens with YOU, from them YOU may buy, and from their families that are with YOU whom they had born to them in YOUR land; and they must become YOUR possession. 46 And YOU must pass them on as an inheritance to YOUR sons after YOU to inherit as a possession to time indefinite. YOU may use them as workers, but upon YOUR brothers the sons of Israel, you must not tread, the one upon the other, with tyranny."
Summary-The Israelites were allowed to buy slaves from other nations, and then hand them down as an inheritance.