If you check the Old Testament, you will see that the only cases in which God recommended polygamy was when a woman was left widowed without children. In that case, the brother of the widow's deceased husband was to become her husband and thus provide children to care for her in her old age. In God's economy, the valid purpose of polygamy was to care for the widow. Jesus made it clear that any situation other than "one man, one woman, joined inviolate" was a variance from His absolute righteousness, and that included polygamy.
It became clear through scripture by the time of Christ that every other case of polygamy noted in scripture resulted in discord and unhappiness, even if God eventually turned the situation to His good. By the time of Jesus, polygamy had become rare among Jews.
And also, by the time of Jesus polygamy was already prohibited by law among Romans and Greeks--the people to whom Paul preached.
So you're actually incorrect when you assert that polygamy was a righteous state even then.
There is a whole discussion on polygamy over in a different thread if we were to discuss the particulars, which I am not inclined to do. Here was one I saw:
Is polygamy a sin
My main point is that a man having more than one wife was not considered adultery. A woman having more than one husband would have not only been considered adultery, but against natural law and called wickedness.
Therefore due to these types of distinctions you can not neuter discussions on marriage, adultery and remarriage and call it good because the rules were always different. I will give two quick biblical type examples of how that could go wrong in a hurry:
A married man’s brother died and he takes his deceased brother’s wife to give his brother offspring, according to the law. His first wife tries to say that is adultery and leaves him and marries another....she is incorrect in her assessment.
A married man commits fornication with a virgin...the virgin’s family demands that he marry her. The mans first wife calls this adultery and drags him to the council saying he should be put to death for adultery...she is incorrect in her assessment.
My only point I am making on this, is not what is perfect, but that you cannot neuter the verses and think it’s all good, it doesn’t work that way, and it never has. But today this seems to slip people’s attention.
Even today there could be men who have multiple wives who come to the faith (this isn’t fanciful, many Muslim men have multiple wives and could convert to Christianity). It would be incorrect to tell him he is committing adultery. You can’t neuter the verses. If a woman today came to the faith, while having multiple husbands...she would have to make a change, that is not acceptable, and never has been. Again, my entire point, you can’t make these verses gender neutral and call it good.
And now back to Jesus’ words on marriage, adultery and remarriage. Based on what I mentioned, keep the genders in place, on his words, and on all the New Testament scriptures pertaining to this subject.
Also this brings up a good point, we must have an answer for the huge multitudes of men with multiple wives (there are hundreds of millions of Muslims, near two billion, it’s not an obscure thing) who will come to the Christian faith. With the churches current common gender neutral teachings on these subject it could lead to some dire mistakes, for instance if a person recommends he abandon all but his first wife, and leave them destitute. We must have an answer for these issues, and cannot make huge mistakes here.
