When President Obama threw his support behind same-sex marriage, he did something much more than please the members of the LGBT community and the people who love them.

He gave hope and encouragement to millions of Americans struggling to do right by their children in unconventional or nontraditional families by implicitly asserting “as a practicing Christian” that using the Bible as a literal handbook for raising healthy, happy kids is retrograde, insensible and wrong.

This Mother’s Day, Obama’s declaration gives gay and lesbian couples, as well as interracial couples, infertile couples and single parents — as well as every mother who fears she’s not doing it right — a reason to rejoice.

For too long, the Bible has been used to stigmatize and censure people who fail to adhere to approved norms. “Shame, despair, solitude!”: This was the plight of Hester Prynne, the heroine of Nathaniel Hawthorn’s “The Scarlet Letter,” after conceiving a child outside of marriage. But norms change and are, in any case, not approved by God. Such is the consensus of the faithful, in retrospect, about the Bible’s acceptance of slavery.

Religious conservatives may argue otherwise, but as I pointed out in a 2008 Newsweek article, “The Religious Case for Gay Marriage,” the Bible offers no examples of what might be called “the traditional family.” The patriarchs in the Hebrew Bible were polygamists. The great King David seduced his neighbor’s wife. Jesus himself was unmarried and valued his community of faithful brothers and sisters in God above his earthly family. The apostle Paul was celibate and saw marriage as a last resort for those who found it impossible to control their sexual desires. “It is better to marry than to burn with passion,” he wrote.

And while Scripture fails to offer modern families reasonable role models, it also prohibits and punishes not just sex between men but so much of modern domesticity that few of us would escape the judgment of a biblical jury. And when the Bible is opaque, humans are all too willing to fill in the picture.

Scripture, for example, was used to support anti-miscegenation laws. “Almighty God created the races white, black, yellow, Malay and red and placed them on separate continents, and but for the interference with his arrangement there would be no cause for such marriages. The fact that he separated the races shows that he did not intend the races to mix,” wrote Judge Leon Bazile, in Loving v. Virginia in 1965. Today, more than 8 percent of American marriages are mixed race, up from 3 percent in 1980.

The shame of Scripture’s infertile women — Hannah prays for a miracle — has trickled up through the ages. The idea of fertility as an extension of God’s will both torments today’s infertile couples and is cited as an argument against in vitro fertilization. According to the catechism of the Catholic Church, artificial means of conception are “morally unacceptable” because “they disassociate the sexual act from the procreative act.” Yet at last count, three million babies have been born to infertile parents worldwide since 1976.

But of all the biblical prohibitions, perhaps none is as stringent as the one against sex outside marriage. The seventh commandment prohibits adultery, and Deuteronomy establishes the crucial importance of virginity — for women — before marriage (under penalty of death). But according to the Guttmacher Institute, nine in 10 women have had sex before marriage.

Today, 40 percent of births are to unmarried women and a third of children live in single-parent homes. Single-mother households, like the kind in which Obama grew up, may not be biblically approved, but they are increasingly the rule, not the exception.

The Bible’s wisdom may be eternal and its stories and teachings eternally mined for broad lessons about God’s justice and love. Together, the Hebrew Bible and the gospels emphasize family love and respect, fidelity in marriage and to God. The Scriptures teach about welcoming strangers and caring for the “widows and orphans,” the weakest members of society.

Obama’s faith and his moral compass have pointed him to the inevitable conclusion: On the specifics of what constitutes a “good” or “right” kind of family, the Scriptures offer no guidance at all.

To read Lisa Miller’s previous columns, go to washingtonpost.com/onfaith