A man could have more than one wife in the OT, Deuteronomy 21:
2 Samuel 12:
What about in the NT?
English Standard Version 1 Timothy 3:
Deuteronomy 25:15 If a man has two wives, and he loves one but not the other, and both bear him sons but the firstborn is the son of the wife he does not love,
The brother of the dead man could already have a wife of his own and take on one more wife.5 If brothers dwell together, and one of them dies and has no son, the wife of the dead man shall not be married outside the family to a stranger. Her husband’s brother shall go in to her and take her as his wife and perform the duty of a husband’s brother to her.
2 Samuel 12:
God not only permitted David to have multiple wives but also gave him wives. True?8 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.
What about in the NT?
English Standard Version 1 Timothy 3:
1 Corinthians 7:2 Therefore an overseer must be above reproach, the husband of one wife, sober-minded, self-controlled, respectable, hospitable, able to teach.
It seems that polygamy was permitted in the OT but discouraged in the New. Matthew 19:2 But since there is so much immorality, each man should have his own wife, and each woman her own husband.
8 Jesus replied, “Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning.