Some of the canonical gospel texts on divorce seem to me to be somewhat out of context with the biblical times when they were purported to have been written, as if possibly inserted. The focus on monogamy seems out of place. There are other places in the gospels where Jesus refers to a husband and multiple bridegrooms in parables.
I think Jesus’s time was a time when it was common for men to have many wives, and for wives not to have a say in to whom they were married. In many parts of the Muslim world today, this is still the case. Although divorce is allowed in Muslim culture, the terms are pretty unequally distributed and a woman divorces her husband with much more difficulty than a man divorces his wife (khula or خلع ). In orthodox Jewish communities even today, women without a prenuptial agreement can become agunot, “chained”, with both parties unable to remarry, because their husbands will not give them a get. Only 1000 years ago did rabbinic Judaism change marriage to be one husband and one wife. The only reasons for a man to divorce during earlier times then would be that his wife had done something to dishonor him, or because he did not want to support her, or because he might go to war and disappear leaving her in an unknown state as to whether or not he was alive. He could marry as many people as he could support (admittedly since Jesus mostly preached to the poor – this may have been just one family). He was not forced to technically live with any of his wives (and could sequester them, supporting them without interaction with them until their death if he so chose). The theological question then arose as to what happens in heaven upon death, when a woman remarries in this life, and her former husband is waiting for her in the afterlife. Who has the right to her in the afterlife? At which point, I believe, that Jesus taught that the concept of marriage did not apply in the afterlife. Since many people are happily married, this is a source of sadness to them. They want their spouses in the afterlife.
Gospel texts on divorce such as Matthew 19:1-12 sometimes occur within the context of a confrontation with the Pharisees (defenders of Mosaic law), which explains their reactionary tone. There are corollaries in Matthew 5:27, Mark 10:18 and Luke 16:18. Each is slightly different. In Mark 10:18, women can divorce men and become unclean. In Matthew 5:27 and Luke 16:18, the definition of uncleanliness (adultery) extends beyond the marital bond to the community. In Luke, it does not include the woman. She, being voiceless, cannot be responsible. It is every man’s responsibility not to remarry the divorced woman. In Matthew 5:27, the woman can be charged with the sin, but the husband is responsible. Only in Mark 10:18, is a tone of balance between the sexes struck, and she can be responsible. As pointed out by Marten Krijgsman in “Divorce in the New Testament”, each account has a slightly different attribution of the uncleanliness, and therefore who must atone. Canonical John 7:53-8:11 alone has the story of the adulteress who is spared stoning, although it may not have been included in very early versions of this gospel.
Eventually, from a theological perspective, one has to decide how to protect the integrity of the soul throughout relationships, and how much to sanctify the institution of marriage. The institution evolved as an issue of property – who belongs to whom, and how are resources regulated, during a time when the discussion was really among men because for the most part, women could not own property. Sometimes, even whole households were killed when the man died. Later this was probably deemed to be cruel and they were subsumed by the man’s brother or relative if he had one. It occasionally fell to society as “a mitzvah” to be kind to the widow, etc. (see the mitzvot 40, 79, 80, 81, 180, 385, 386 from http://www.jewfaq.org/613.htm).
Although ancient Jewish texts are replete with the language of monogamy, polygamy it seems was considered a right of power. The legality of polygamy in Jewish culture is mentioned in Josephus’s texts around Jesus’s time. One possibility is that, knowing the strife and jealousy that can exist among wives, texts on ethics tended to be written (politely) for one wife, in order not to dilute the importance of relationship ethics with ideas of outside conflict. My understanding is that, about 1000 years ago, Rabbi Gershom banned polygamy, and this ban stuck in Ashkenazi but not Sephardic communities (Rabbi Silberberg).
So, in a world where women have rights, how does one redefine relationship property rights? The integrity of the soul is maintained through consensual relations, and honoring commitments that are made to one another. It is also maintained, as my good friend pointed out, by not stoning anyone in the community. Marital commitments (like any other commitment), although they can be sealed with G_d’s name and also annulled, may not require such sanctification if one decides that marriage is a matter for this life, and not the afterlife.