The term pilegesh appears to be an Indo-Europeanloanword related to παλλακίς pallakis, meaning concubine. In Modern Hebrew, pilegesh is often used as the equivalent of English "mistress"—i.e. the female partner in extramarital relations even when these relations have no legal recognition.
Biblical references
Several biblical figures had concubines when they were not able to create natural children with their wives. The most famous example of this was with Abraham and Sarah. Sarah gave her maidservant Hagar to Abraham while maintaining ownership of both maidservant and offspring. Their union produced Ishmael. Hagar gained the status of full wife in regards to Abraham, but nonetheless Sarah retained the status of main wife. This type of pilegesh is recorded in Jewish sources as being a singular case. All later cases of pilegesh recognized the pilegesh and guaranteed similar rights in the house as the legitimate wife. Since having children in Judaism was considered a great blessing, legitimate wives often gave their maids to their husbands so they could have children with them when those women themselves were childless, as in the cases of Leah and Zilpah and Rachel and Bilhah. The concubine commanded the same respect and inviolability as the wife, and it was regarded as the deepest dishonor for the man to whom she belonged if hands were laid upon her. Even in the exceptional case of Sarah and Hagar, Abraham would have been obligated to treat Hagar as a full wife and she would have been treated as an equal by Abraham. Sarah's rights would have been regarding the technical legal status of being considered the inheritor and since the other wife and offspring would have been hers by ownership she became the legal albeit not biological mother of Ishmael.
According to the Babylonian Talmud, the difference between a pilegesh and a full wife was that the latter received a marriage contract and her marriage was preceded by a formal betrothal, which was not the case with the former. According to Rabbi Judah, however, the pilegesh should also receive a marriage contract, but without including a clause specifying a divorce settlement. Certain Jewish thinkers, such as Maimonides, believed that concubines are strictly reserved for kings, and thus that a commoner may not have a concubine; indeed, such thinkers argued that commoners may not engage in any type of sexual relations outside of a marriage. Maimonides was not the first Jewish thinker to criticise concubinage; for example, it is severely condemned in Leviticus Rabbah. Other Jewish thinkers, such as Nachmanides, Samuel ben Uri Shraga Phoebus, and Jacob Emden, strongly object to the idea that concubines should be forbidden. Any offspring created as a result of a union between a pilegesh and a man were on equal legal footing with children of the man and his wife. According to Rabbi Mnachem Risikoff, the institution of pilegesh is an alternative to formal marriage which does not have the same requirements for a get upon the dissolution of the relationship.
