Matthew places this teaching during the time Jesus was in Judea leading up to His Last Passover. It's a very hard teaching that a great many church folks would prefer to ignore.

The Pharisees approached Jesus to dispute with Him about something He had said not long ago, criticizing the Pharisees for trading wives like domestic livestock. So they asked Him whether the Law permitted them to divorce a wife for just about any reason or excuse a man chose. This was pretty much what their oral traditions said, but Moses was intended to be more strict than that.

Jesus cut to the heart of the problem. When you look at the Creation narrative, God made man and woman, and intended them to stay together for life. The teaching was plain: two shall become one flesh. This is a miracle of God, not some human choice. People can choose not to marry, but once wed, God has wired them to imprint on their first sex partner. Once that imprint is made, it can never be broken. It can be abused and forsaken, but it can never be broken. This is well known medical fact.

This is what Jesus is talking about. God made us this way. We are supposed to imprint and never part. Obviously we are supposed to be very careful about whom we propose to marry. It's not a frivolous social convenience, but a total change of heart. You now belong to someone for life. Any subsequent partner gets a broken spouse, and it will weaken the bond between the two.

You cannot undo this. You could try to ignore it at your peril; doing so would defile you in God's eyes, another aspect Jesus mentions here. So, the Pharisees ask: Why would Moses give such a low standard? Jesus said it was because the Israelis were particularly hard-hearted toward God's ways. But Moses' weak command was not the standard starting from the Garden of Eden.

Jesus then reinforced this teaching by warning that in the Father's eyes, divorce and remarriage made former spouses into adulterers. This was no small matter.

Once the debate was ended, the Twelve remarked that this was indeed a very high standard. This being so very hard, maybe it was better not to marry. Jesus responded that this kind of thing was only possible by divine calling. If God doesn't give you the conviction to live like this, you won't be able to do it.

He goes on the mention that there three kinds of eunuchs: those born that way, those made that way by third parties, and those who voluntarily chose it in order to keep peace with God. Without conviction, you could never do it voluntarily.

Whether or not you want to read this as a reference to literal castration or some kind of symbolism doesn't make any difference. In God's eyes, you can have either zero or one sex partner for life. Granted, widows and widowers can justly remarry. However, it's not the ideal situation, because the imprint is still there. The Levirate Law suggests that imprinting is less of an issue with close kin, something otherwise unthinkable. However, the whole question there is a measure of feudalism, something wholly rejected by modern western populations.

Still, this comes from the mouth of the Master Himself. We dare not suggest He didn't mean it to apply to us today. Just because it's so hard is no excuse for ignoring it. Paul goes into this issue at length in his letters, but the fundamental principle doesn't change: If you get this wrong, you will forever lose a part of your shalom that can never be recovered. The best answer is to be very, very careful in choosing to marry in the first place. You only get one shot.

I don't need hands or fingers to count how many Christians I know, personally and not, that have followed the "no remarrying until death" rule: zero. I know some that have "fulfilled" it, but likely it was by accident/circumstance.

It's not as if there can be no good reason to marry again -- conviction still plays a role -- but church folks give today give the most frivolous excuses with zero acknowledgement of the danger.

This thread seems  a plausible place to ask the following follow-up question.

If God intended for our marriage experience to be one man, one woman, for life, why are the instances of men with multiple concurrent wives not called out more clearly as "wrong".

On the one hand I think of several instances where it worked out poorly: Abraham, Jacob, Samuel's dad, Solomon. There is even Jewish/Hebrew law that says a man should not take his wife's sister as a marriage partner while his wife is still alive, but that seems to be a narrow law to me, not prohibiting all multiple-concurrent-wife situations.

But then on the other hand we have David with multiple wives, and he was called a man after God's heart, and his only named failure was Uriah and Bathsheba (which was adultery and then murder - 2 Samuel 12:7-13).

In none of these instances, with "good" or "bad" results, are any of these men called out for the "sin" of having a second wife as far as I know.

What gives?

Jesus explained it pretty well. He said the issue was divorce, and then pointed out that it was supposed to be one man, one woman for life. He didn't even mention polygamy, but still excluded it. In His day, polygamy wasn't much of an issue. There was a long history of polygamy in the ANE, so the tolerance for it was very high early in the OT. As time went on, that tolerance faded. But divorce arose as a serious problem.

Jesus said the underlying problem was the hardness of heart. That kind of fault can certainly come from cultural biases. Up through the Bronze Age, ANE culture permitted polygamy. Somewhere during the Iron Age, it faded. We see that polygamy almost disappears completely by the time of the Return from Exile. It's like a lot of other things we see in the Bible. Not every failure of human nature was present during Jesus' day, so He didn't have to mention it. Homosexuality wasn't a Hebrew problem, but it was something that loomed large later on when the gospel spread among Gentiles. So, we see it taught in Paul's letters, but the New Testament also has its own historical issues that are different from what we face today.

Scripture tends to report what actually happened, warts and all. We aren't told directly that Judah sinned when he checked in with what he thought was a prostitute, but was his daughter-in-law laying a trap. She knew his tendencies. We know it was a sin, but the story is simply told, and we see the consequences. You and I can look back and see that polygamy was a mistake.

We are supposed to see it from where we are now, but we are also supposed to understand why it was a sin. Our culture tolerates divorce, so there's a whole lot of it. We don't tolerate polygamy so much, so it's not an emphasis for us. If we can drill down to the underlying moral truths, we may have a tough time putting them into words, but our convictions will translate it for us into our context.

To add a little to why polygamy was big in the OT: that was simply how a lot of women were able to survive, so in a sense polygamy was tolerated as a necessity. To translate it broadly to our modern situation, we could probably pick out something in America that we partake in that would be forbidden in scripture, like usury. Like women and polygamy in the OT, we are "victims" of our situation more than the perpetrator. It's part of how materialist western society is structured. We're not on the hook for it, but our response is. We'll have to use our conviction to see in what ways we can separate ourselves as much as possible from that system.

Thanks for drilling down into that for me. It helps.