I'm simply going to resubmit my reflection on this from last year since the readings are repeating.
Today’s gospel passage from Mt 19:1-9, along with its only parallel in Mark 10 (other than Luke’s brief addition of 16:18), are the entire basis for the Church’s teaching on the indissolubility of marriage. From Matthew’s version of this teaching of the Lord’s we can see from the reaction of his disciples, that it was as difficult to hear then as it often is today.
Mark’s account makes it virtually impossible to ignore Jesus’ understanding here. First, he tells the Pharisees that only the “hardness of their hearts” led Moses to grant divorce. Then he states categorically, “What God has joined together, no one can separate.” Finally, as if to completely remove any possibility of ambiguity or misunderstanding of his intent, he tells his disciples privately and bluntly, that for either party to divorce and remarry, is to commit adultery.
Matthew’s account is basically the same except for the famous “Exception Clause” found there in Mt 19:9. However, there is much debate about exactly what the Lord meant by this. The long and the short of it seems to be that Jesus clearly forbade divorce and remarriage. The only possible alternative, the one the Church uses today, is to determine that there never was a valid marriage in the first place due to various situations that are judged to have invalidated it from the beginning. We call this annulment of the marriage. It might be seen as falling under Jesus’ giving Peter the keys to the Kingdom of Heaven, in that this is part of what he allowed the Church to “loose” on earth.
Given all that, there are some other things to consider here. First, the Lord quotes two verses from Genesis. The first is Gen 1:27, “So God created humankind in his own image, in the image of God he created them; male and female God created them.” The second is from Gn 2:24, “That is why a man leaves his father and mother and is united to his wife, and they become one flesh.” The prior quote is from the first of the two creation accounts in Genesis known as the Priestly Account (there are two completely distinct creation accounts combined in Genesis from two distinct original sources). In that account (the one that begins Genesis) there is no Adam and Eve, where Eve is (secondarily) created from Adam’s rib. The Adam and Eve story of creation in Genesis, known as the Yahwistic Account, is the source of Jesus’ second quote from Genesis in today’s reading. It is this second Yahwistic Account that has very much influenced the belief that the male gender of humanity is somehow the principal gender while the female is derivative of (and therefore somehow subservient to) the male. This was certainly the belief of everyone (male and female) in the ancient Palestine of Jesus’ time. It was a thoroughly patriarchal society that no one questioned.
Therefore, that Jesus cites the Priestly creation account in reference to his understanding of marriage seems quite telling of his rather radical understanding, it seems, of marriage in his day (and in our day too, actually). For there, in that account, humanity was not created first male and only secondarily female as but a help to the (principal) man, but rather, from the very beginning (i.e., always) humanity was created male and female. No subordination is implied here. Rather, the implication by Jesus definitely seems toward equality.
Yet in Jesus’ time, there most definitely was no equality. Women had almost no rights by law other than those granted them by their husbands. They could neither own or control property on their own. They had no authority in religion or the state. They were excluded from most activities and work and largely expected to remain in the home. Neither was it at all easy for a Jewish woman to divorce her husband, where conversely, it was extremely easy for the husband to divorce his wife. And by divorcing her, she could be left destitute and without means should her family not receive her back. Surely something of that injustice had to influence the Lord’s forbidding divorce. It was for the sake of the married women.
Another thing to consider is that Jesus saw marriage as a spiritual union that triumphed over the “flesh.” They become one in marriage. Such a reality cannot be possible without a strong, shared spiritual foundation of faith in and reliance upon God. For the Lord, it must have been that marriage, as he saw it, could make no sense outside the love of God the married couple shared in completely and their mutual devotion to that love expressed in their devotion to themselves. That is why it has always been compared to Christ’s love for the Church where he gave himself up completely for her.
For Jesus, the love the married couple has for one another is meant to be both from God and like God’s love for us. Thus, both partners are willing to give everything to and sacrifice everything for the beloved. Without that, it is not really a marriage in the Lord. As Jesus would tell his disciples in Matthew 19, “Those (does it imply “only those”?) who can accept this, should accept it!” Is it really any wonder then, why so many marriages end in divorce?