Yesterday a couple of friends posted this:
So what is the bible's definition of marriage?
Abraham married his father's daughter by another mother and sent his servant to find his son Isaac a wife from among his kin. The servant came back with Isaac's cousin, who Isaac married.
About 4 or 5 centuries later, in Leviticus, God forbids marrying half-sisters, which would make Abraham's marriage illegal. There is no prohibition against marrying cousins, so while his parents would have been in a forbidden relationship, Isaac would have still been fine under Levitical law.
Later, King David had either four or five wives (it's not clear) and sometime after he died, God is quoted as saying, "Have you considered my servant David? He is perfect." Polygamy was perfect (well, for a man) in Old Testament times. David's son Solomon certainly seemed convinced of this. He had 700 wives (and somehow still found time for 300 concubines).
A man could also get a divorce and re-marry. Jesus speaks out against that practice in the New Testament. Curiously, he doesn't speak out against the practice of polygamy, although this somehow seems implied, It would make little sense to ban someone from re-marrying if they could marry more than one woman at a time.
Paul went further than Jesus. Jesus thought it was wrong to re-marry and Paul thought it was wrong to marry. He wasn't exactly a champion of family values, holding that it made little sense to marry given the world was about to end. But he seemed to grudgingly accept that some people would be unable to live without companionship and intimacy and thought that marriage was the best place to find such solace.
What, then, is the bible's definition of marriage? Something that was evolving. Just like it is today.