Genesis 6:19 And of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female. (KJV)
Genesis 7:8-9 Of clean beasts, and of beasts that are not clean, and of fowls, and of every thing that creepeth upon the earth, There went in two and two unto Noah into the ark, the male and the female, as God had commanded Noah. (KJV)
Genesis 7:2 Of every clean beast thou shalt take to thee by sevens, the male and his female: and of beasts that are not clean by two, the male and his female. (KJV)
Considering that these are from the same book (and within a 13-passage section), the idea of a true contradiction is unlikely. The Genesis 6:19 passage is telling the number that Noah had to bring on the ark in order to keep them alive (for a species to reproduce, they only need a male and a female). In Genesis 7:2, the number ofclean animals that are to be brought is upped to seven because now God is ordering Noah to bring animals for food and sacrifice. Genesis 7:8-9, it's simply saying that they entered the ark two by two, and says nothing about the idea that there were only two of each type of beast. Not a contradiction.