'Clean' in the Bible

You are to take with you seven pairs of every clean animal, a male and its mate, and two of the unclean animals, a male and its mate;

From both clean and unclean animals, from birds, and from everything that crawls on the ground,

Then Noah built an altar to the LORD and offered burnt offerings on it from every clean animal and every clean bird.

Didn't he say to me, "She's my sister'? And she also said, "He's my brother.' I did this with pure intentions and clean hands."