Is it lawful...?
Beginning preachers often assume that only after they have built up the trust of the congregation by assuring them of God's lovingkindness will they have earned the right to deliver the harder words of scripture. They quickly discover that the opposite is the case: congregations are grateful to preachers who tackle hard or unpopular biblical texts with exegetical care and pastoral sensitivity. Preachers who win a congregation's trust by doing so are more likely to be heard and believed when it is time to preach good news that seems too good to be believed: the forgiveness of sins and the resurrection of the dead.
But how to approach Jesus' strict teaching about divorce and remarriage as it appears in Mark's Gospel, without the somewhat more lenient amendments of Matthew and Paul? Most congregations contain people who are married (happily and unhappily), people who are divorced (some of whom are remarried) and people who have not married for various reasons (including the fear of failure and divorce). Clearly the point of the gospel is not to reopen old wounds or to increase feelings of guilt or failure; therefore neither should the sermon do that.
A good starting place might be a review of Deuteronomy 24:1 and its interpretation during Jesus' time. Both marriage and a man's right to divorce were assumed in Judaism; what was debated were the grounds for divorce. The law says that if the wife "does not please him because he finds something objectionable about her," then he can write her a certificate of divorce. There were several schools of thought about what constituted "something objectionable": one school said it was enough if she burned his dinner; another insisted on serious and substantial reasons for divorce. Mark's Gospel remembers that Jesus' opinion was sought on this controversial topic and remembers it in a context (Rome?) that seems to assume a woman's legal right to separate from or divorce her husband as well.
What is striking about Jesus' answer is that he redirects the issue from what is lawful or allowed to what God has intended from the beginning about marriage. Quoting from both creation stories in Genesis 1 and 2, Jesus stresses permanence, exclusivity and God's initiative. "The two" called into marriage are to leave behind even their parents to become joined in mutual support and affection. Jesus' conclusion—"What God has joined together, let not human beings separate"—can be read either as a pronouncement or as a plea. Some marriages implode from within; others are sabotaged by external forces. Marriages require community support to flourish.
The pressures on a marriage are intense. I once praised a couple for their long marriage, only to hear one of them say, "It is only by the grace of God that we have remained married all these years" and to see the other nod and laugh in agreement. The "hardness of heart" Jesus warns about is not limited to married people, and it certainly isn't limited to those who have experienced the agony of a failed marriage. Nevertheless, marriage is hard work, and the continuing softening of our hearts towards one another over time is one of God's greatest gifts. No wonder the early church fathers and mothers taught that marriage, like monasticism, is a training ground for the reign of God.
Perhaps that is why this passage is paired with the story about Jesus welcoming and blessing the little children over the objection of the disciples. The reign of God is open to those who receive it the way a little child receives it—as sheer gift to those with no power, no rights, no demands, no status and no sense of their own achievement.
Whether we have married or not, whether we have succeeded in marriage or failed or some of each, we are not rejected children. We are not kept away from Jesus. We are loved, welcomed and blessed by the God who made us, both male and female, for God's own self. What God has so joined together, no human being can ever separate.