IS INCEST FORBIDDEN?

Deuteronomy 27:22  Cursed be he that lieth with his sister, the daughter of his father, or the daughter of his mother. And all the people shall say, Amen. (KJV) Genesis17:15  And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be. (KJV) Genesis 20:12  And yet indeed she (Sarah) is my sister; she is the daughter of my father, but not the daughter of my mother; and she became my wife. (KJV)

In the days of the Israelites, marriage or sexual intercourse with your sister was forbidden.  As for Abraham and Sarah, they were not really brother and sister.  In Genesis 20:12, Abraham is lying out of fear, claiming that Sarah was his half-sister, when she was actually his wife.  Many will point to the fact that the children of Adam and Eve obviously committed incest, but incest was not forbidden at that time.  For a further explanation, go to this page about Cain and Seth.  Not a contradiction.