Let's try for a minute to take the religious conservatives at their word and define marriage as the Bible does. Shall we look to Abraham, the great patriarch, who slept with his servant when he discovered his beloved wife Sarah was infertile? Or to Jacob, who fathered children with four different women (two sisters and their servants)? Abraham, Jacob, David, Solomon and the kings of Judah and Israel—all these fathers and heroes were polygamists. The New Testament model of marriage is hardly better. Jesus himself was single and preached an indifference to earthly attachments—especially family. The apostle Paul (also single) regarded marriage as an act of last resort for those unable to contain their animal lust. "It is better to marry than to burn with passion," says the apostle, in one of the most lukewarm endorsements of a treasured institution ever uttered. Would any contemporary heterosexual married couple—who likely woke up on their wedding day harboring some optimistic and newfangled ideas about gender equality and romantic love—turn to the Bible as a how-to script?
from Newsweek's cover story on Marriage and the Bible. I recommend reading the whole article.