Today I was debating with a Christian who believes in polygamy and claimed that the Early Church Fathers allowed for the act of polygamy, is that true and is there any evidence that the Early Church condemned the act of polygamy (ie marriage to more than one spouse at a time).
Did the Early Church Fathers condemn polygamy?
The short answer is yes.
Tertullian (155-220), wrote that marriage is lawful, but polygamy is not:
We do not indeed forbid the union of man and woman, blest by God as the seminary of the human race, and devised for the replenishment of the earth and the furnishing of the world, and therefore permitted, yet singly. For Adam was the one husband of Eve, and Eve his one wife, one woman, one rib. We grant, that among our ancestors, and the patriarchs themselves, it was lawful not only to marry, but even to multiply wives. There were concubines, too, (in those days.) But although the Church did come in figuratively in the synagogue, yet (to interpret simply) it was necessary to institute (certain things) which should afterward deserve to be either lopped off or modified. For the Law was (in due time) to supervene. (Nor was that enough:) for it was meet that causes for making up the deficiencies of the Law should have forerun (Him who was to supply those deficiencies). And so to the Law presently had to succeed the Word of God introducing the spiritual circumcision. Therefore, by means of the wide licence of those days, materials for subsequent emendations were furnished beforehand, of which materials the Lord by His Gospel, and then the apostle in the last days of the (Jewish) age, either cut off the redundancies or regulated the disorders. - Marriage Lawful, But Not Polygamy.
Justin Martyr, Irenaeus and Tertullian all spoke against polygamy, condemning it. Tertullian explicitly tackled the objection that polygamy was allowed for the patriarchs.
The monogamy of the Roman Empire was the cause of two explanatory notes in the writings of Josephus describing how the polygamous marriages of Herod the Great were permitted under Jewish custom.
Some of The Dead Sea Scrolls show that several smaller Jewish sects forbade polygamy before and during the time of Jesus.
Although some have argued that St. Paul may have seemingly allowed polygamy in some cases except for bishops or church leaders. This is in direct conflict with Church Fathers and not a Catholic interpretation of the Sacred Texts. They make mention of 1 Timothy 3: 1-5. Many critics of polygamy also point to the Pauline epistles that state that church officials should be respectable, above reproach, and the husband of a single wife (1 Timothy 3,Titus 1).
The Greek phrase mias gunaikos andra is an unusual Greek construction, capable of being translated in multiple ways, including (but not limited to): 1) "one wife man," (prohibiting plural marriage) or 2) "a wife man" (requiring elders to be married) or 3) "first wife man" (prohibiting divorcés from ordination).
1 Timothy 3: 1-5:
1 It is well said, When a man aspires to a bishopric, it is no mean employment that he covets. 2 The man who is to be a bishop, then, must be one with whom no fault can be found; faithful to one wife, sober, discreet, modest, well behaved, hospitable, experienced in teaching, 3 no lover of wine or of brawling, courteous, neither quarrelsome nor grasping. 4 He must be one who is a good head to his own family, and keeps his children in order by winning their full respect; 5 if a man has not learned how to manage his own household, will he know how to govern God’s church?
1 Fidelis sermo: si quis episcopatum desiderat, bonum opus desiderat. 2 Oportet ergo episcopum irreprehensibilem esse, unius uxoris virum, sobrium, prudentem, ornatum, pudicum, hospitalem, doctorem, 3 non vinolentum, non percussorem, sed modestum: non litigiosum, non cupidum, sed 4 suæ domui bene præpositum: filios habentem subditos cum omni castitate. 5 Si quis autem domui suæ præesse nescit, quomodo ecclesiæ Dei diligentiam habebit?
1 Πιστὸς ὁ λόγος: εἴ τις ἐπισκοπῆς ὀρέγεται, καλοῦ ἔργου ἐπιθυμεῖ. 2 δεῖ οὖν τὸν ἐπίσκοπον ἀνεπίλημπτον εἶναι, μιᾶς γυναικὸς ἄνδρα, νηφάλιον, σώφρονα, κόσμιον, φιλόξενον, διδακτικόν, 3 μὴ πάροινον, μὴ πλήκτην, ἀλλὰ ἐπιεικῆ, ἄμαχον, ἀφιλάργυρον, 4 τοῦ ἰδίου οἴκου καλῶς προϊστάμενον, τέκνα ἔχοντα ἐν ὑποταγῇ μετὰ πάσης σεμνότητος: 5 εἰ δέ τις τοῦ ἰδίου οἴκου προστῆναι οὐκ οἶδεν, πῶς ἐκκλησίας θεοῦ ἐπιμελήσεται.
Paul only prohibits it for church leaders.
In his letter to Timothy, Paul writes:
Therefore an overseer must be above reproach, the husband of one wife, sober-minded, self-controlled, respectable, hospitable, able to teach, not a drunkard, not violent but gentle, not quarrelsome, not a lover of money. He must manage his own household well, with all dignity keeping his children submissive, for if someone does not know how to manage his own household, how will he care for God’s church?
1 Timothy 3:2-5
Given that this letter was written in the context of a polygamous culture, it can therefore be reasoned that Paul wasn't prohibiting polygamy entirely, but only banning polygamists from attaining positions of power in the church, along with banning those in power in the church from abusing that power to accumulate multiple wives.
I don't know what other early church fathers said in writings outside the Bible, but it's my understanding that strict monogamy was a primarily Greek and Roman thing at the time of the early Church, it entered the Church through Greek and Roman converts, and that the Catholic Church eventually enforced it on Medieval kings in order to gain political power over them by controlling their wedding alliances. I don't have any citations for that, though.
"Appendix A: Authorities Referenced at [the Council of] Trent" of Brugger's The Indissolubility of Marriage and the Council of Trent, pp. 149-99, cites many who directly or indirectly condemn polygamy by reaffirming the indissolubility of marriage.
A succinct one is (ibid., p. 153):
It is not licit for you if your wife still lives to take another wife. For indeed to seek another when you have your own is the crime of adultery; this is most serious, because you think in your sin that you should seek freedom in the law [to divorce].
Non licet tibi, uxore vivente uxorem ducere. Nam et aliam quaerere, cum habeas tuam, crimen est adulterii, hoc gravius, quod putas peccato tuo auctoritatem lege quaerendam.