Why were the slaves held in captivity for 7 years?

Answer 1

If you were thinking of ancient Israel then captivity is a poor choice of word as the system there was you (or a relative) could enter someone's service for 6 years as payment of a debt you owed to that person. You could also enter into this type of arrangement if you were unemployed and unable to support yourself. While in both cases technically you were a slave, it was more a form of indentured employment and by law you had to be well treated and cared for by your employer and in the 7th year they had to not only release you from your obligation, but also to set you up with money and/or goods so you could reestablish yourself back in free society. Another type of arrangement that is translated as "slavery" for wont of a better word was when a father who could not afford a dowry to secure a good marriage for his daughter, might "sell" her into a well-to-do family in order to ensure her future security. The "sale" presupposes marriage to the master or his son and The Torah stipulated that the girl must be treated as a free woman and should the designated husband take an additional wife, he is still obligated to support her for the rest of her life. Last but not least, there were no jails in those times so there were only two ways of dealing with criminals, including war criminals - you either executed them or detained them under a conscription/forced-labor arrangement. This is not too dissimilar to what we do with convicted criminals today. None of these arrangements comes even close to what we think of as slavery today and could not be more different from the slavery that was practised by other nations including America.