As two spies blow their cover, they are surprisingly protected by a Canaanite woman named Rahab.  Why? Because she had experienced a transformation and her faith was now in the God of Israel.  As a result, her house would be marked by God and she wold be preserved. Rahab appears in the genealogy of Jesus because he is the ultimate fulfillment of this story. We find refuge in Jesus and are marked by God and welcomed into this family.