I echo the question by John Wells. I also find some things particularly interesting about Deuteronomy 24. Let's take a look at it...
Deut 24:1 "When a man takes a wife and marries her, and it happens that she finds no favor in his eyes because he has found some uncleanness in her, and he writes her a certificate of divorce, puts it in her hand, and sends her out of his house, 2 when she has departed from his house, and goes and becomes another man's wife, 3 if the latter husband detests her and writes her a certificate of divorce, puts it in her hand, and sends her out of his house, or if the latter husband dies who took her as his wife, 4 then her former husband who divorced her must not take her back to be his wife after she has been defiled; for that is an abomination before the LORD
Let's look at Luke 16 again.
Luke 16:18 "Anyone who divorces his wife and marries another woman commits adultery, and the man who marries a divorced woman commits adultery.
Again, here are the contrasting views of the same principle in Luke 16:18:
1. If you divorce your wife and marry another woman, you commit adultery.
2. If you marry a divorced woman, you commit adultery.
If the above really is meant to convey that the principle applies to the woman as well as the man, then why doesn't it say this:
"Anyone who divorces his wife and marries another woman commits adultery, and any woman who divorces her husband and marries another man also commits adultery." That would be a more natural way of expressing that sense of "they're both in the same boat", wouldn't it? Yet that's not what Jesus said. Why not, if this interpretation is correct?
Deuteronomy 24 answers that question. There is no provision for the woman to divorce her husband. So the only way to word the comparison would be the way Jesus worded it -- from the perspective of a divorced woman in BOTH cases. It's adultery if you divorce a woman and marry another, and it's adultery if you marry a divorced woman. You got between one of two people who were still one flesh with each other at the time, therefore you commited adultery. But are they still one flesh with each other after one or both of them have commited that adultery?
Now -- let's add in that "exception clause" (emphasis mine).
Matthew 5:32 But I tell you that anyone who divorces his wife, except for marital unfaithfulness, causes her to become an adulteress, and anyone who marries the divorced woman commits adultery.
Matthew 19:9 I tell you that anyone who divorces his wife, except for marital unfaithfulness, and marries another woman commits adultery."
Why would Jesus make marital unfaithfulness an exception? How does that fit with the Mosaic law? Let's look at the relevant section of Deuteronomy:
if the latter husband detests her and writes her a certificate of divorce, puts it in her hand, and sends her out of his house, or if the latter husband dies who took her as his wife, 4 then her former husband who divorced her must not take her back to be his wife after she has been defiled; for that is an abomination before the LORD
To paraphrase the section: If the woman is divorced and marries another, and then her new husband divorces her or dies, then she must NOT remarry her first husband -- that is an abomination. In other words, not only is the first husband no longer bound to his first wife after she remarries, he is FORBIDDEN to marry her again even if her new husband dies. Something about her becoming "one flesh" with another man has forever altered her relation to her former husband.
Now re-read Matthew 5:32 in light of that...
Matthew 5:32 But I tell you that anyone who divorces his wife, except for marital unfaithfulness, causes her to become an adulteress, and anyone who marries the divorced woman commits adultery.
Matthew 19:9 I tell you that anyone who divorces his wife, except for marital unfaithfulness, and marries another woman commits adultery."
Obviously, "marital unfaithfulness" means someone became "one flesh" with another person, right?