Question: I was asked this question by a new Christian: Why did God allow people in the Old Testament to marry multiple wives?
Response: In Matthew:19:4-5, the Lord Jesus states, "And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female, and said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain [two] shall be one flesh?" Not "they three, or four, or five, etc.," but "they two." Jesus is reiterating the intent of God. Our Creator designed marriage to be between one man and one woman for life. The first disagreement to this intent came from Lamech (Gn. 4:19), who had two wives. Lamech was of the cursed line of Cain, which all perished in the flood.
Speaking of the kings of Israel, the Lord God commanded, "Neither shall he multiply wives to himself, that his heart turn not away..." (Dt 17:17). Those that have authority have high standards. As such, we are not surprised to see that regarding church leadership, Paul wrote that "A bishop then must be blameless, the husband of one wife, vigilant, sober, of good behavior, given to hospitality, apt to teach" (1 Tm 3:2).
Yes, David and Solomon had many wives. Do we envy the disaster this brought? The envies, murders, and hatred in David's family is hardly an endorsement for polygamy. Speaking of Solomon, the Scriptures note: "And he had seven hundred wives, princesses, and three hundred concubines: and his wives turned away his heart" (1 Ki:11:3).
No one can produce one Scripture purporting to indicate that the Lord approved of polygamy. Much like divorce, it was "tolerated" but never "approved." Of divorce, the Lord Jesus noted, "He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so" (Mt 19:8). Again, what is in focus is "in the beginning." What did God intend? The biblical focus is never what man has made of the Lord's original intent.
In conclusion, any usage of biblical texts to support polygamy must of necessity fly in the face of Scripture, a process the apostle addressed in 2 Peter:3:16 where "they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction."