This is just in the Old Testament. It was a practice in those days Many of Muhammad’s marriages He never bore children and they were clearly political marriages to create peace between tribes and to protect rhe women from slavery, starvation and prostitution.
Abraham had more than one wife. You believe in Abtaham don’t you?
In Exodus 21:10, a man can marry an infinite amount of women without any limits to how many he can marry.
In 2 Samuel 5:13; 1 Chronicles 3:1-9, 14:3, King David had six wives and numerous concubines.
In 1 Kings 11:3, King Solomon had 700 wives and 300 concubines.
In 2 Chronicles 11:21, King Solomon’s son Rehoboam had 18 wives and 60 concubines.
In Deuteronomy 21:15 “If a man has two wives, and he loves one but not the other, and both bear him sons…”
There are a lot more verses from the Old Testament that allow polygamy, but I think that the above are sufficient enough to prove my point.
Here’s an interesting question by a Christian and look at the answer given.
Question: “Why did God allow polygamy / bigamy in the Bible?”
Answer: The question of polygamy is an interesting one in that most people today view polygamy as immoral while the Bible nowhere explicitly condemns it. The first instance of polygamy/bigamy in the Bible was that of Lamech in Genesis 4:19: “Lamech married two women.” Several prominent men in the Old Testament were polygamists. Abraham, Jacob, David, Solomon, and others all had multiple wives. In 2 Samuel 12:8, God, speaking through the prophet Nathan, said that if David’s wives and concubines were not enough, He would have given David even more. Solomon had 700 wives and 300 concubines (essentially wives of a lower status), according to 1 Kings 11:3. What are we to do with these instances of polygamy in the Old Testament? There are three questions that need to be answered: 1) Why did God allow polygamy in the Old Testament? 2) How does God view polygamy today? 3) Why did it change?
So, it seems that God may have allowed polygamy to protect and provide for the women who could not find a husband otherwise. A man would take multiple wives and serve as the provider and protector of all of them. While definitely not ideal, living in a polygamist household was far better than the alternatives: prostitution, slavery, or starvation.
You can study in depth here from a Christian viewpoint
gotquestions.org/polygamy.html