The Law that Moses gave also made provision for plural marriage and in some cases, it seems that plural marriage was even commanded by the Law of Moses. There is evidence that multiple wives was an acceptable practice all through ancient Israel, including the time of Christ and it was not until the end of the 1st Millennium AD that some Jews officially rejected polygyny. One branch of Jews never agreed to this and still accept the practice of plural wives to this day. Many people suppose that a concubine is someone not really married to the man, whereas the wife is the one who is married. However, in 1 Chron.
Many experts agree that the term was particularly used to describe second class wives.
Children of wives were sons of the patriarch and they obtained full inheritances from their fathers. Children of concubines were sons of the concubine and had no inheritances, though they received gifts during the lifetimes of the patriarchs. But unto the sons of the concubines, which Abraham had, Abraham gave gifts, and sent them away from Isaac his son, while he yet lived, eastward, unto the east country. He also blessed Abraham exceedingly shortly after the second marriage. Again Abraham took a wife, and her name was Keturah.