'Clean' in the Bible

You are to take with you seven pairs, a male and its female, of all the clean animals, and two of the animals that are not clean, a male and its female,

From the clean animals, unclean animals, birds, and every creature that crawls on the ground,

Then Noah built an altar to the Lord. He took some of every kind of clean animal and every kind of clean bird and offered burnt offerings on the altar.

Didn’t he himself say to me, ‘She is my sister’? And she herself said, ‘He is my brother.’ I did this with a clear conscience and clean hands.”