The first recorded polygamist was Lamech who took unto himself two wives (Genesis 4:19).
Adultery is the sinful intercourse of a person with someone who is not his one lawful and Scriptural marriage partner. It was forbidden in the Jewish law (Exodus 20:14) and was punishable by death (Leviticus 20:10). Polygamy is merely adultery on a permanent basis. Polygamy is always adultery, but adultery is not always polygamy, the origin of these two words was different, fornication being the sin of unlawful intercourse by an unmarried person, and adultery the sin committed by a married person. But in New Testament usage the words several times are used to mean the same thing (see Revelation 2:20-22). Therefore, adultery and fornication are essentially the same sin according to the Bible meaning. It might be said that they are different forms of the same sin.
We find in the New Testament says that marriage to another partner while the first partner is still living is adultery (Romans 7:1-3). No fornicator or adulterer shall inherit the kingdom of Elohim (1 Corinthians 6:9,10). Since a polygamist is an adulterer, he cannot inherit the kingdom of Elohim, 1st Corinthians 7:2 says, "Let every man have his own wife, and let every woman have her own husband." Polygamy is sinful for male or female. Women married to the same husband do not each have their own husbands, 1st Corinthians 6:9,10 lists many types of sinners, including fornicators and adulterers. As noticed above, a polygamist is actually an adulterer (Romans 7:1-3). Then 1 Corinthians 6:11 says, concerning the members of the church at Corinth, "And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Master Yahshua, and by the Spirit of our Elohim." These adulterers and fornicators had repented and been cleansed from their past life by obeying the Scriptures. If all types of sinners could be cleansed in Corinth, all types, including polygamists, can be cleansed if they repent and obey as did the people of Corinth, we must remember that repentance is a change of mind which results in a change of life (Matthew 21:28,29).
Before a person is baptized for the remission of sins, he must believe in Yahshua (Mark 16:16), confess his faith in Yahshua (Acts 8:37), and repent of his sins (Acts 2:38). Without real faith, without a sincere confession of his faith, and without real repentance, baptism does not bring remission of sins. To be baptized without repentance cannot bring forgiveness (Acts 2:38), we find that the sin of polygamy must be repented of in the same way as any other sin. The polygamist changes his mind, heart, and life. He turns away from all his sins and turns to Yahshua, the Savior from all sin. He reverses his entire life and determines to change every sinful practice.
But his repentance is not real unless he brings forth the fruits of repentance (Luke 3:8). This means putting away all wives except the true one. Just as a thief must give up stealing, so must a polygamist give up polygamy, or else his repentance is not sincere, and his baptism is worthless. A man's first wife is his rightful wife unless she was already the rightful wife of another man when he married her. The first wife a man marries is his only Scriptural wife. All others are merely women living with him in adultery (Romans 7:1-3). In order to genuinely repent, he must therefore put away all other women except his first rightful wife, sin always bring serious problems. Prevention is always better than cure. The above question states one of the serious difficulties resulting from the sin of polygamy; True repentance is never easy because it requires undoing the sinful conditions of one's sinful life. The prodigal son got up out of the country of riotous living and returned humbly and broken-heartedly to his father's house (Luke 15:17-20). In like manner a polygamist must penitently forsake the conditions of his sin and return to Elohim's love. When he does this, Elohim will surely assist him in putting away his adulterous wives in a fair and honorable way. Furthermore, he will either care for his children himself or will render a father's rightful support of them in their mother's care.We can find in 1st Timothy 3:2 requires that each of the bishops (or elders) in each congregation must be "the husband of one wife." Elders are examples to all the flock or congregation (1 Peter 5:3). A corrupt member (especially a leader) may corrupt the whole church (1 Corinthians 6:1,6). A polygamist must not be asked to lead prayer, as "holy hands" must be lifted up in prayer (1 Timothy 2:8). They must not be asked to serve as treasurer or to do any other work, as this may make them think that they have approval. A polygamist can no more serve as a leader in the church than can a murderer or a thief.
We also find that Elohim made one wife, Eve, for Adam (Genesis 2:22). Elohim's plan since creation has been that one male and one female, "the twain" (or two), become "one flesh" (Matthew 19:4-6). From the beginning, Elohim never intended for men to put away their wives or to marry additional wives. Men began these practices because they rejected Elohim's plan out of the hardness of their hearts (Matthew 19:8). During the Old Testament Elohiim allowed many practices of the Israelites which He never planned nor approved. One such thing was a king, but He allowed a king in order to let them see for themselves the foolishness of departing from His way (1 Samuel 8). In like manner, additional wives were allowed to the Israelites because of the hardness of their hearts, but not because such was Elohim's plan or Elohim's will.
Also consider Romans Chapter 7, We know Elohim did not divorce the house of Judah. why didn’t Elohim divorce them? So I ask how could Elohim break his own marriage law and have a son by a woman to whom he was not married? Some people have told me because Elohim can do anything. That is not true. Because Elohim can Not sin! He remained married to the house of Judah so that his son would be legitimate. But the marriage to the house of Judah did not continue forever. When Yahushua died on the stake the marriage to the house of Judah ended. That is partly what Romans chapter 7 is about. http://www.lwmlc.com/re-marriage.php
was never good for Abraham or any other Old Testament polygamist. Hagar caused jealousy, strife, and trouble until she was expelled from Abraham's house (Genesis 16:4; 21:9-11). Likewise, the wives of Solomon caused great difficulties and turned his heart away from the Lord (1 Kings 11:3,4). Polygamy in the Old Testament strongly shows us the wisdom of God's plan for one wife and the foolishness of man's way of additional wives. Since God made man, He knows the best plan for man's marriage and home.