Technically, the form of marriage being discussed is most precisely called "polygyny", where one man marries more than one woman at the same time. Many of the leading men of the Bible had more than one wife in some form of marriage relationship at the same time. This includes Abraham, Jacob (Israel), Moses, David and others. 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.

Wives and Concubines

As we discuss this, we should keep in mind that the Bible describes both "wives" and "concubines". Many people suppose that a concubine is someone not really married to the man, whereas the wife is the one who is married. This is a modern usage for the word "concubine" and is not how it was used anciently. That the word "concubine" means "wife" in ancient times is shown by some examples from the Bible:

• In Gen. 25:1, Keturah is called Abraham's wife. However, in 1 Chron. 1:32 Keturah is called a concubine.

• In another instance, Nathan, the prophet tells David, "I will take thy wives before thine eyes, and give them unto thy neighbor, and he shall lie with thy wives in the sight of this sun" 2 Sam. 12:11. later in the same book, the fulfillment of this prophecy is recorded: "And Absalom went in unto his father's concubines in the sight of all Israel;" (2 Sam. 16:22)

Thus, the term "concubine" in the Bible appears to be synonymous with "wife", though it is only applied to plural wives. Many experts agree that the term was particularly used to describe second class wives. This "second class" status was important for inheritance. 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. Thus we read:

And Abraham gave all that he had unto Isaac. 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. (Genesis 25:5-6 )  

Abraham Married 3 Women

The first patriarch that the Bible shows in a plural marriage relationship is Abra(ha)m. In Genesis 11:29 we find the account of Abra(ha)m being married to Sara(i/h):

And Abram and Nahor took them wives: the name of Abram's wife [was] Sarai; and the name of Nahor's wife, Milcah, the daughter of Haran, the father of Milcah, and the father of Iscah.

However, Sara(i/h) was barren and had no children. To alleviate this situation and provide an heir for her husband, Sara(i/h) gave her husband a second wife:

"And Sarai, Abram's wife, took Hagar her maid, the Egyptian,…and gave her to her husband Abram to be his wife;" (Gen. 16:3)

The Lord was evidently not displeased for in speaking of the child of this polygynous marriage he said, "I will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget and I will make him a great nation;" (Gen 17:20). He also blessed Abraham exceedingly shortly after the second marriage.

In addition to the marriage to Hagar, Abraham also took another wife:

     Again Abraham took a wife, and her name was Keturah. (Genesis 25:1)

Thus, Abraham had three wives: Sarah, Hagar, and Keturah. Abraham, considered in the Bible to be the "friend of God", was held up by both Jews and Christians as the example of a good and faithful life.  

Abraham's Grandson was Jacob. He served Laban seven years for Rachel, but Laban deceived him, and Leah became his wife instead. So he served another seven years for Rachel. He married them both and they were both wives. The account of this service, Laban's deception and the two marriages can be found in Genesis 29:18-35 and 30:3-12. In addition one can also read about how each of these wives had a handmaid and Jacob was given each of these handmaids as concubines and they also had children by him. Thus Jacob had four wives according to scripture.

Jacob was renamed Israel by the Lord and by each of these four women, he had children. In all, from these four wives, he had 12 sons who became the Patriarchs of the 12 Tribes of Israel. The sons who obtained the most significant blessings were Judah and Joseph. Judah was the son of the first wife, Leah and Joseph was the son of the second wife, Rachel.  

Moses, after fleeing Egypt, was in the land of Midian. There "he sat down by a well" where "seven daughters" of the "priest of Midian" "came and drew water". (Exodus 2:15-16). After protecting these daughters from some attackers, Moses became a house guest "and Moses was content to dwell with the man: and he gave Moses Zipporah his daughter." (Exodus 2:21)

However, we find that Moses did not just marry this Midianite woman named Zipporah. We do not know the name of his second wife, but we know it happened because the scriptures say " he had married an Ethiopian woman." and this marriage was of concern for some unstated reason to his sister. (Numbers 12:1).

Thus Moses was married to at least two women.  

David, king of Israel took Abigail and Ahinoam, "and they were also both of them his wives;" (1 Sam. 25:42-43). Then he "took him more concubines and wives out of Jerusalem;" (2 Sam. 5:13). With two wives and concubines (plural) he at this time had at least 4 wives. The Bible later says that "David did that which was right in the eyes of the Lord, and turned not aside from anything that he commanded him all the days of his life, save only in the matter of Uriah the Hittite;" (1 Kings 15:5). In this passage we have an assurance that David done right in taking all his wives and concubines, except in one instance, for which he was severely chastised. In the case of Uriah the Hittite, David committed adultery with his wife, and then had Uriah killed in the Battlefield. This was adultery and murder and it was condemned by the Lord, but his prior marriages were, according to the Bible, approved as "right in the eyes of the Lord".  

From the evidence of the Bible, plural marriage was not uncommon in Israel. Not only did these previously mentioned patriarchs and great men of Israel have more than one wife, but it is clear that other lesser individuals did as well. At least 10 individuals are also recorded in the Bible as having had more than one wife:

Judges 8:30 Gideon, a man highly favored of the Lord, had three score and ten sons and many wives.
Judges 9:5 Jerubbaal had seventy sons, which would be impossible without polygyny.
Judges 10:3-4 Jair, a judge in Israel, had thirty sons.
Judges 12:13-14 Abdon, a Judge in Israel, had forty sons.
I Sam 1:1-2 Elkanah had two wives. His son, Samuel, was a great prophet, and judge in Israel. He was born, and lived under the special favor of God.
1 Chron. 4:5 Ashur, the father of Tekoa, had two wives.
1 Chron. 8:8  Shaharaim had two wives.
2 Chron. 11:21 Rehoam had eighteen wives and three score concubines.
2 Chron. 13:21 Abijah married fourteen wives.
2 Chron. 24:3 Jehoida, the priest of God, took two wives.

In every instance shown above, plural marriage is not recorded as something exceptional or strange, but as rather ordinary and commonplace. The statements are made in an off-hand matter-of-fact manner. Thus, it is no surprise when respected Orientalists such as W. M. Flinders Petrie in speaking about ancient Hebrew marriages says: "polygamy was usual" (W. M. Flinders Petrie, Egypt and Israel, p. 24.)  

When Moses took a second wife, he was not in violation of the Law given to him by the Lord. That law does not prohibit plural marriage and in fact, recognized the possibility of multiple wives:

If a man have two wives, one beloved, and another hated, and they have born him children, both the beloved and the hated; and [if] the firstborn son be hers that was hated: then it shall be, when he maketh his sons to inherit that which he hath, that he may not make the son of the beloved firstborn before the son of the hated, which is indeed the firstborn. (Deuteronomy 21:15-16)

In fact, the Law of Moses sometimes may have commanded Plural Marriage. When a woman's husband died, the Lord commanded that a brother of the husband was supposed to take her as his wife. (Deut. 5:4-10.) If he was already married, then at that point he would have had two wives. The Law as given to Moses does not mind that.  

Plural marriage was still acceptable among the Jews in the days of Jesus. In fact, he uses a plural wedding in one of his most famous parables:

Then shall the kingdom of heaven be likened unto ten virgins, which took their lamps, and went forth to meet the bridegroom. And five of them were wise, and five were foolish. They that were foolish took their lamps, and took no oil with them: But the wise took oil in their vessels with their lamps. While the bridegroom tarried, they all slumbered and slept. And at midnight there was a cry made, Behold, the bridegroom cometh; go ye out to meet him. Then all those virgins arose, and trimmed their lamps. And the foolish said unto the wise, Give us of your oil; for our lamps are gone out. But the wise answered, saying, Not so; lest there be not enough for us and you: but go ye rather to them that sell, and buy for yourselves. And while they went to buy, the bridegroom came; and they that were ready went in with him to the marriage: and the door was shut. Afterward came also the other virgins, saying, Lord, Lord, open to us. But he answered and said, Verily I say unto you, I know you not. (Matthew 25:1-12)

Interestingly, Martin Luther, recognizing that Jesus did not condemn and may have subtly condoned polygyny, later declared Polygyny to be an acceptable Christian practice.  

In the various Diaspora periods, Jewish customs changed. Over time, plural marriage became less common generally among European Jews. About the year 1000, Rabbi Gershom ben Judah reportedly issued an edict (Herem de-Rabbenu Gershom) which was considered authoritative among Ashkenazi Jews. This edict substantially prohibited plural marriage. One exception was allowed: A man could marry more than one wife if he obtained the special permission of 100 rabbis in 3 countries. Originally, Gershom's ban was limited in time to the year 1260, however it has continued to be accepted by Jews of Europe and the Western World to this day.

However, Rabbi Gershom's ban was not accepted by all Jews. In particular, Shephardic Jews (Yemenite Jews for example), still take plural wives though in most cases this is limited to four according to the custom of the surrounding Moslem culture. Culture is significant in this question for Jews. Where custom allows such things, the Jewish laws tend to go along.

An interesting example is the modern Jewish State of Israel. Generally speaking, Israel does not allow new plural marriages, but polygynous families who immigrate can continue to live in plural marriage arrangements. Israel today makes plural marriage a criminal offense. However, even under this restriction there are some cases that allow for plural marriage:

"for Jewish citizens (of Israel) no offense is committed if permission to marry a second wife was given by a final judgment of a rabbinical court and approved by the two chief rabbis of Israel. The latter's approval is accepted as conclusive proof that the permission was given according to the law. Special provisions relating to the grant of this permission are laid down in the Takkanot ha-Diyyun be-Vattei ha-Din ha-Rabbaniyyim be-Yisrael, 5720-1960." (Howard Landman, Jews and Polygamy)  

Mormons and Plural Marriage

The Church of Jesus Christ of Latter-day Saints, sometimes called "Mormons", practiced plural marriage from the early 1840's to about 1890 when they were forced to stop by the Federal Government. Latter-day Saints felt that in following this style of marriage they were submitting themselves to God's will and following the example of Abraham, the "friend of God". Many outside the LDS faith have ridiculed this practice, often with the hidden presumption that it is highly immoral or licentious. Perhaps unacceptable by many westerners today, the evidence is clear that the ancient patriarchs married multiple wives. Arguments or statements ridiculing or deriding Latter-day Saints, if applied to Israel's patriarchs would be very disrespectful of Judeo-Christian history. Thus, a fair question could be: If God did not condemn this practice in the Bible and if the Latter-day Saints were doing so in sincere devotion to God, what Christian or Jew has the right and authority to judge their moral integrity in this matter?