This Bible contradiction is from the Skeptic's Annotated Bible.
Genesis 6:19 View context
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.
Genesis 7:8 View context
Of clean beasts, and of beasts that [are] not clean, and of fowls, and of every thing that creepeth upon the earth,
Genesis 7:2 View context
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.