Polygamy, as used in this Bible study, is defined as one man being married to more than one woman, or one woman married to more than one man. Strictly speaking, the Old Testament practice of one man having multiple wives at one time is known as polygyny. An important fact to remember regarding polygamy is that it has fundamentally always been something that only rich men could take advantage of, since maintaining such a large family was expensive.
The Old Testament is clear about its view regarding polygamy. Although God himself ruled Israel when they came out of Egypt, he knew there would likely be a time when they would want a human king over them. Although He warned any future Israelite king that they should not possess MANY wives, He did not command that they must have only one (see Deuteronomy 17:14, 17). Additionally, what few realize, is that no passage exists that forbids multiple wives among Israel's tribes.
God knew the kings that would ultimately be over his people would pursue polygamy like all the other nations around them. He warned them not to have many wives, especially those from outside the twelve tribes of Israel (pagans), so that they would be less likely to be lead away from him. Unfortunately, men like King Solomon did not follow this advice. Although he was wise, he nevertheless married many foreign women who turned his heart away from the Eternal (see 1Kings 11).
By the time of the early church, the general practice of polygamy had largely died out in the Roman Empire. Although the Romans themselves did not practice it, they did divorce and remarry when they wanted to change spouses (serial monogamy). A few exceptions existed such as Herod the Great, who was a polygamist. Although the New Testament does not directly address this marital arrangement, the fact that it says almost nothing about the practice points to its decline, even elimination, among God's people.
There are several Scriptural-related passages on marriage, in the writings of Paul, which strongly infer that polygamy was not an acceptable practice among Christians. For example, he wrote to Timothy that one of the traits to look for in a good church leader was that he was "the husband of one wife" (1Timothy 3:2, 12). He also wrote this admonition to Titus as well, who was preaching the gospel and helping believers on the Island of Crete (Titus 1:5 - 6). The church in Corinth was told one way to help avoid sexual immorality was to ensure that each person had one mate (1Corinthians 7:2).
The book "The Moral Sense" states that the practice of one man having multiple wives at the same time has steadily declined over time. Writing about this decline in the world he states, "The ground was prepared for the growth of individualism and universalism by the dramatic changes that occurred in family life during some thousand years, stretching from the end of the Roman Empire to the Renaissance. In this time, monogamous marriages triumphed over polygamy . . . and gradually shifted its focus away from parental and kinship concerns (e.g. arranged marriages) . . ." (Page 205).
What should Christians do in regard to polygamy? They should submit to the laws in the land they live in so long as they do not conflict with what God's word teaches (see Romans 13). A large percentage of countries in the 21st century have laws against such marital arrangements (with the exception of countries governed or influenced by Islam). Modern-day believers should reject this ancient practice of multiple mates and stick to one woman for one man.