There are 33 direct references to polygamy in the Bible, with almost all references being in the Old Testament and only passing reference in the New Testament. Why the sudden change? Likely because the purpose of the New Testament was entirely different.
So when it comes to understanding the Bible's position on polygamy, we have to rely almost entirely on the Old Testament.
We'll quote the relevant verses below, as well as discuss likely or known context.
Polygamy in the Old Testament
Polygamy in the New Testament
The New Testament differs greatly on the subject of marriage. Not so much in relation to polygamy, but because the focus is on the bond and duties between husband and wife rather than a recounting of historical events.
In fact, all references to marriage seem to be ambiguous, at best, if they are referencing monogamy or polygamy.
For example, Ephesians 5:28 says "So ought men to love their wives, as their own bodies: he that loveth his wife, loveth himself."
This quote may very well be referencing monogamous marriage or polygamy, given the wording.
For this reason, we are left to rely on the New Testament for direction on marriage but the Old Testament for quotes involving polygamy.
Conclusion
What you will notice with all of the biblical quotes referencing polygamy is that there is neither approval or condemnation. Rather, being polygamous is mentioned as a detail relevant to the individual or events, sometimes in relation to the most favored individuals in the Bible.
God does not appear to have been shy about rendering a verdict on a wide range of subjects, so why the lack of direction on polygamy?
You will find many people pursuing polygamy and claiming that it was ordained by God. We won't make any claim so bold, nor do we think it is especially true.
We would argue that marriage, as a sacred bond, was ordained by God. And if you study the judgments made in relation to marriage, stories told, as well as the direction and commandments given, they all relate to not betraying those you have sworn yourself to and have an obligation to serve.
Whether that's between a man and woman or a man and his many wives does not seem important in scripture.
It's the actions of the individual that one will be judged on, whether you are a loyal servant to your wife or many wives.