Besides free hired laborers, the Jews, like all other nations of the time, also employed slaves; but the form of slavery which prevailed among them was not so harsh or cruel as that in the Roman empire. The old law allowed a Hebrew reduced to poverty to sell himself as a slave to another Hebrew. But this did not last for life, only for a term of six years; in the seventh year he was entitled to his liberty if he liked, and his master was enjoined to give him a handsome present for his service. If he desired, however, to remain a slave (and this shows that slaves might become strongly attached to their masters, Exod. Xxi. 5), he could be formally devoted to servitude for the rest of his life. Afterwards another arrangement was introduced by the transfer of the time of liberation to the jubilee, every fifty years; and no option was given to the bondman under the later law to remain a slave: no member of Yahweh's people could permanently part with his liberty. So the slave-markets of the great cities of the Mediterranean were unknown in Palestine.
from pages 52-53, Life in Palestine
from pages 52-53, Life in Palestine