("that [kidnapper]": to exclude one who steals one who is half-slave-half-free.)
"the thief": to include as liable one who steals his son and sells him. These are the words of R. Yochanan b. Beroka. And the sages say: One who steals his son and sells him is not liable.
"and you shall remove the evil from your midst": Remove the doers of evil from Israel.
(Devarim 24:8) "Be heedful of the plague-spot of leprosy": This is a negative commandment.