The first thing to know is that there is no prohibition against polygamy in Bible, either Old or New Testament.
In non-Muslim countries people cannot have more than one wife at any one time simply because of legal restrictions. Also, there are ecclesiastical prohibitions in many churches.
But if we look in the Scriptures, being honest with ourselves and with God, we do not find there a prohibition against having more than one wife.
It would be better, of course, if each of us had one couple: one husband or one wife. Then, as soon as men and women are roughly equal in number on earth, there will be no deprived, non-family. We should think not only of our own and our families’ good, but also of the good of others. But there are different situations in life.
The same goes for the command to live without entertainment:
35 I say this for your own benefit, not so that I may put you in bondage, but so that you may serve the Lord without amusement. (1 Corinthians 7:35),
(1 Corinthians 7:35) understanding what amusement they are talking about: even one couple is allowed in Scripture only as an exception, to avoid fornication:
1 But of what you wrote to me, it is good for a man not to touch a woman.
2 But, [for the avoidance of] fornication, each one shall have his own wife, and each one shall have his own husband. (1 Corinthians 7:1,2).
But the problem is different in churches: there are many more women and girls who believe in the Lord than there are men and boys. Several times over. Practically everywhere. And I think those sisters who today cannot find a mate and are tormented by loneliness would be better off if polygamy were allowed in our countries and churches. This would include the avoidance of fornication.
Besides, many righteous men, according to Scripture, had many wives: Abraham, Jacob, David, and other righteous men. Not only were they not guilty, but by faith and obedience to God they were set an example for the people of God.
The legitimacy of polygamy is also evidenced by God’s commandments, which God gave specifically for families with more than one wife:
15 “If a man has two wives, one the favorite and one the unlovely, and both the favorite and the unlovely will bear him sons, and the firstborn will be the son of the unlovely.
16 And he may not, when he divides his estate among his sons, give to the son of the wife of the favourite the firstborn before the firstborn son of the unloved;
17 But the firstborn he shall give to the son of the unloved one a double portion of all that he hath; for he is the firstling of his strength, to whom belongs the right of the firstborn. (Deuteronomy 21:15-17).
Here God teaches how to deal with children of different wives.
18 You shall not take a wife together with her sister, to make her a rival, to reveal her nakedness in her presence, in her lifetime. (Lev.18:18).
Here God forbids you to take your wife’s sister with your wife. Though before this commandment came Jacob had taken his sisters, Rachel and Leah, for himself. But he was not guilty, for the law has power over those under the law who are under the law:
19 But we know that the law, if it speaks anything, speaks to those under the law, so that every mouth is shut, and the whole world becomes guilty before God, (Rom.3:19).
And Jacob was not yet under the law: the law was given a few hundred years later, under Moses.
10 But if another shall take for him, she shall not be deprived of food, raiment, or marital intercourse; (Exodus 21:10).
Here God forbids the second wife to be deprived of her basic needs and marital companionship.
There may be other commands in the law where God speaks of polygamy. There is no point in citing them all.
Also, the brother-in-law is legally obligated to take his dead brother’s widow for himself after his brother dies, whether he already has a wife or not:
5 If brothers live together, and one of them dies without having a son, the wife of the deceased shall not go out to marry a stranger, but her brother-in-law shall go in to her and take her as his wife, and live with her,” (Deuteronomy 25:5).
An example of such a blessed marriage is the marriage of Boaz and Ruth (Book of Ruth). Although it is not known if Boaz had a wife other than Ruth. But he was already in his old age at the time.
So, it is legal according to the Bible to have more than one wife.