For the principal purpose of marriage according to the Bible, Keller draws upon Paul’s discussion in Ephesians 5:21-33 and argues that marriage was essentially designed for our sanctification. Marriage, he suggests, “is for helping each other to become our future glory-selves, the new creations that God will eventually make us (p. 120).” Keller argues from Ephesians 5:25 that just as Christ loved the church and gave himself for her, so too spouses should follow Christ’s example. Christ, moreover, gave himself up for the church to sanctify her that he might present the church holy and blameless. Keller infers a direct parallel to both spouses not just in the nature of Christ’s love expressed, but also the goal of that love, namely to sanctify his bride, the church, in perfect holiness. But is such a parallel warranted by the text? The parallel in 5:25 is between how husbands are to love their wives and how Christ loves the church. Keller extends an imperative specific to the husbands to include both the husband and the wife eliminating any complementary distinction between husband and wife, while simultaneously bypassing the exhortations specific to wives in 5:22-24 and 5:33. He acknowledges this jump in a footnote (n8 p. 262) and simply suggests that since all Christians are to hold each other to account for spiritual growth generally, wives must also do this for their husbands. But given that sanctification is already an inherent part of Christians relationships generally independent of marriage, it hardly seems compelling that the specific purpose for which marriage was designed is our sanctification.
But should the parallel in the goal of Christ’s love, in its perfectively sanctifying effects, even be granted in the case of husbands? The text in 5:24-27 speaks of Christ sanctifying his church through the single sacrificial act of his death. This one time act sanctified the church cleansing her through washing that she might be presented as completely holy and blameless. The unique nature of Christ’s accomplishment is underscored in the choice of the simple undefined aspect of the aorist tense for each associated verb. On the other hand Paul uses the continuous present tense for the love expressed by the husband. The husband is to continually love his wife following the model by which Christ offered himself sacrificially once-for-all on behalf of his bride. To infer a direct parallel between the once accomplished positional sanctification completed in Christ and the on-going perfecting process of sanctification that occurs among husbands and wives living the journey of faith is strained at best. Nothing that the husband can do for the wife can remotely compare to the all accomplishing perfecting work of Christ on our behalf. Surely the parallel Paul intends in Ephesians 5:24-27 is in the magnitude of the sacrificial love expressed. So great was Christ’s love for his bride the church that he gave himself in this fashion. In the same fashion, so great ought the husband’s love for his wife that he too continually gives himself up completely and sacrificially. Christ is the model of the depth and extent of the type of love the husband is expected to express for his wife.
But there is much more at stake in suggesting that the biblical purpose of marriage is sanctification than is first apparent. What Keller fails to clarify in his historical-cultural analysis is that the real contrast between ancient views of marriage and modern post-Enlightenment views of marriage is that earlier views always placed the procreation and welfare of the next generation at the forefront of the purpose of marriage. Yes, social status and provision for old-age were also part of it, but the ultimate purpose was to raise up an heir, who would succeed you. What post-Enlightenment individualism has encouraged us toward is a new definition of marriage that focuses entirely on the welfare of the present generation—the husband and wife, irrespective of children at all. The Bible also describes God’s design of marriage for the purpose of procreation. Even before the first marriage is depicted in Genesis 2, God blesses humankind as male and female (Genesis 1:27-28) with the command, “Be fruitful and multiply”. Jesus reiterates this divine intent in Luke 20:34-36 where he makes clear that the sons of this age marry but those who attain to the resurrection do not, because they do not die anymore. No death means no need for procreation, no need for procreation means no marriage. Marriage was designed by God requiring male and female because its fundamental purpose was to provide for the procreation and welfare of the next generation. This is fundamental not accidental to the design of marriage.
The major problem with Keller’s view is two-fold. First, in suggesting the purpose for marriage is sanctification the focus is entirely upon the husband and wife—thus Keller himself in a very true sense still reflects the modern perspective rather than corrects it. Second, if the ultimate purpose of marriage is sanctification, there is no compelling reason why it must be male and female. Males can serve to sanctify each other outside of marriage, so why not inside of marriage? In other words, Keller’s “biblical” purpose for marriage contains nothing inherent in it that requires it to be male and female. Our sanctification may be one of several secondary purposes for marriage, but it cannot be elevated above what the very fabric of biblical creation points to as the supreme purpose of marriage—namely, a divinely appointed institution to foster the continuance of humankind in the present age.