I would argue that the word 'slave' is never mentioned in the Old Testament, and that the term is anachronistic because you cannot have unfree until you have defined freedom. There was no concept of a 'free person' before 5th century Greece. The Israelites in the OT are not 'liberated' from Egypt according to the book of Exodus but 'brought out' to 'serve' God. They go from one service to another. They go from harsh service (an idea which is present in the OT) to good service, but everyone in the OT was an 'eved (servant) of someone else. Even the king was an 'eved. It was not possible to avoid this status. One can plot the creeping presence of 'eved = slave in Bible translations in European languages and in dictionaries over the last 100 years, but this does not stem from careful semantic analysis.
~ Peter J. Williams, Tyndale House, University of Cambridge