“Based on one of the qualifications for elders that a man must be ‘the husband of one wife’ (1 Timothy 3:2; Titus 1:6), were some first century Christians polygamists? Can Christians today be polygamists?” In short, the answers to these two questions are “maybe” and “no.”
Religiously, the first century was a period of transition from Judaism (and Patriarchy for non-Jews) to Christianity. As an example, the apostle Paul and other Christians evidently had initiated Jewish vows at a time when Judaism was effective, but they fulfilled those vows after Judaism was no longer God’s religious law in effect and after the commencement of Christianity (Acts 18:18; 21:23). Since Judaism and Patriarchy have both been replaced with Christianity about two millennium ago, the transition between Judaism and Patriarchy has long since ceased.
Polygamy was practiced by some under both Judaism (e.g., Solomon, 1 Kings 11:3) and Patriarchy (e.g., Abraham, Jacob). Polygamy, though, was not God’s ideal plan for marriage, evident from His creation of one man for one woman—Adam and Eve. The original instructions for marriage only allowed for one husband and one wife (Genesis 2:24-25). During His earthly ministry, Jesus restored God’s original plan for marriage when He was asked about the subject of divorce (Matthew 19:4-5).
Nevertheless, some in the first century may have been polygamists at the time when they became acquainted with the Gospel of Jesus Christ. They, then, found themselves in the situation of having entered into polygamy at a time (under Judaism or Patriarchy) when God tolerated polygamy. It may have been the case that some of these polygamists became Christians, though they had more than one wife at the time.
However, the New Testament teaches that under Christianity, God-approved marriage involves one husband and one wife (1 Corinthians 7:2; Ephesians 5:23). Even if there were some polygamists among first century Christians owing to them having become polygamists when Judaism and Patriarchy were still effective, no one today can be a polygamist and a faithful Christian at the same time, since no one living today ever lived under biblical Judaism or Patriarchy, both of which ended nearly 2,000 years ago. Under Christianity, sexual relations with more than with one’s wife is fornication or adultery and a defilement of marriage (Hebrews 13:4).