Scripture never established concubines or polygamy as an ordained institution, but it did establish marriage between one man and one woman (Genesis 2:24). While Scripture never established polygamy as a viable practice, it never "abolishes" it either. God had to frame some parameters around polygamy to protect vulnerable people from sinful inclinations. He also did the same for divorce and slavery. There were also some man-made laws to protect the abuse of power.
God intended to make “a helper” for Adam, not several helpers.
Let’s look closely at Genesis 2:18–25 and note several key phrases that indicate God’s intent for marriage to be monogamous—one man for one woman. First, God intended to make “a helper” for Adam, not several helpers. Second, from one rib God made one woman for Adam. Genesis 2:24 reveals the pattern of a man leaving his family to “be joined to his wife,” not wives. This union is then described as becoming “one flesh.”
Jesus confirmed this understanding of marriage when he was asked about divorce by the Pharisees. This is recorded in Matthew 19:1–12 and Mark 10:1–12. In his response, Jesus quoted from Genesis 1:27 and 2:24, confirming that marriage was still one man for one woman. Confirming the covenantal nature of marriage, Jesus said that the Mosaic divorce certificate (Deuteronomy 24:1) was only allowed because of the hardness of the hearts of man. God intended, from the beginning, for marriages to consist of one man and one woman for the duration of their lives.
Some have tried to use 2 Samuel 12:8 as an example of God ordaining/sanctioning polygamy. Here’s the verse in the ESV:
And I gave you your master’s house and your master’s wives into your arms and gave you the house of Israel and of Judah. And if this were too little, I would add to you as much more.
God was speaking to David more about the throne and its authority than about wives.
That verse has the Lord’s message to David spoken from Nathan the prophet, and it says how the Lord gave David the wives of Saul. But God’s comments to David through Nathan in 2 Samuel 12 meant that God was speaking to David more about the throne and its authority than about wives. In the Near East at the time of David, it was common practice to either appropriate the wives of a previous king into the royal harem or, if they were much older (and this would have probably been the case with Saul’s wives in regards to David), put them to death along with any of their children, so that no other claim on the throne could be made.
Of course David had promised not to harm any of the house of Saul (1 Samuel 24:21-22, 2 Samuel 9:1), and therefore God’s giving of Saul’s wives to David meant that David actually took care of and protected those who normally would have been disposed of. There is never any mention of David having sexual relations with any of these wives of Saul. They were likely given accommodations at the royal court, but not in the king’s palace, and like Jonathan’s son, Mephibosheth (2 Samuel 9:11-13), were taken care of provisionally.
Looking at a few other English translations of 2 Samuel 12:8, may give us more insight into the meaning and also refute that this was condoning polygamy.
I gave you your master’s house and your master’s wives into your keeping and gave you the house of Israel and Judah. And if that had been too little, I also would have given you much more! (NKJV)
I gave your master’s house to you, and your master’s wives into your arms. I gave you all Israel and Judah. And if all this had been too little, I would have given you even more. (NIV)
I also gave you your master’s house and your master’s wives into your care, and I gave you the house of Israel and Judah; and if that had been too little, I would have added to you many more things like these! (NASB)
And I gave thee thy master’s house, and thy master’s wives into thy bosom, and gave thee the house of Israel and of Judah; and if that had been too little, I would moreover have given unto thee such and such things. (KJV)
First, God mentions that all of Saul’s kingly “possessions,” including his wives, were given to David, then Israel and Judah, and then says he would have even given David much more. Given the order presented, this cannot be referring to just more wives, nor is that the emphasis. Remember that God (through Nathan) had already promised to establish and bless David’s house and kingdom (2 Samuel 7:16)
According to JFB’s Commentary on this verse (2 Samuel 12:8): "The phraseology means nothing more than that God in His providence had given David, as king of Israel, everything that was Saul’s. History furnishes conclusive evidence that he never actually married any of the wives of Saul. But the harem of the preceding king belongs, according to Oriental notions, as a part of the regalia to his successor."
Just as God permitted divorce because of the hardness of men’s hearts, he also limited it.
Just as God permitted divorce because of the hardness of men’s hearts, he also limited it by not allowing a man to remarry a previously divorced wife (Deuteronomy 24:4). There were also instances where a man was not allowed to divorce his wife (Deuteronomy 22:19, 29), especially in cases where he slandered or ruined his wife’s reputation. God had also commanded that kings were not to multiply wives to themselves (Deuteronomy 17:17). Obviously many of the kings of Israel and Judah did not follow this command, and often Scripture records the sad consequences of this sin.
In the New Testament, Jesus forbade divorce except in the case of adultery (Matthew 19:9). Paul (writing through the inspiration of the Holy Spirit) also allowed divorce in the case of an unsaved spouse leaving a Christian spouse (1 Corinthians 7:15). But even here, Paul urged the believing spouse not to seek or initiate the divorce (1 Corinthians 7:12–13).
Keeping in mind that Christians would have been instructed that marriage was for one man for one woman, in accord with Christ’s teachings (in Matthew 19:4-6 and Mark 10:6-9), unmarried converts to Christianity would have subsequently entered into monogamous marriages in obedience. However, for those converts who became Christians while already in a polygamous marriage, the New Testament, by establishing rules for elders and deacons that only men in monogamous marriages could hold office (1 Timothy 3:1–13; Titus 1:5–9), there was even more pressure put upon polygamy to "die out" quickly in the church.
All believers are called upon to emulate the purity and scriptural conduct of their leaders—and this would include their monogamous lifestyle.
We also need to remember that the leaders in the church are told to be examples to the flock, and the believers are told to follow the example of the Apostles, the local elders, and deacons (1 Corinthians 4:16–17, 11:1; Philippians 3:17; 4:9; 1 Thessalonians 1:6,7; 2 Thessalonians 3:7,9; 1 Timothy 4:12; 1 Peter 5:3–5). Therefore all believers are called upon to emulate the purity and scriptural conduct of their leaders—and this would include their monogamous lifestyle. In fact one measure of a godly widow, worthy of support from the church funds, was that she be a "wife of one husband" (1 Timothy 5:9), which further highlights that monogamy was encouraged.
Keep in mind that had God (through the Apostles) instituted a new law, that polygamy must be immediately abolished, then people with multiple wives would have to sin against Christ’s command in order to comply: they would either have to divorce or abandon their "extra" wives. Therefore Jesus (and later his Apostles) restated that it was not what God intended marriage to be, as ordained in Genesis 1 and 2. Later New Testament books set restrictions on Christian offices, and Godly marriage was likened to Christ as husband and the church as his bride, clearly setting a pattern to follow for new Christians.
As the older believers who had multiple wives died off in the early church, the tendency would have been for one man-one woman marriages to become the sole (as God intended) basis of the Christian family. God did not have to abolish polygamy: it died a "natural death" within Christendom. Even today, when polygamous people groups are converted to Christianity, the implemented church policy is often for a gradual phasing out of polygamy. According to an ethical case study prepared for the Meserete Kristos Church in northwestern Ethiopia, consultant Bedru Hussein concluded that following the pattern of early NT church practices1 would be effective in eliminating polygamy. “It may be a matter of one generation that the polygamous relationship will be eventually done away with.”2
But to return to the original question, God definitely did not condone polygamy in 2 Samuel 12:8. In fact when you read the next few verses (2 Samuel 12:9–12), you see that instead of David receiving “even more” blessings, he had forfeited some of those and instead would be punished for his adultery and for the murder of Uriah with public humiliation, divisions, and war within his own household.