And whence is it derived that one who shamed another pays money? It is written here (19:21) "your eyes shall not pity," and elsewhere (in an instance of shaming) (Ibid. 25:12) "your eyes shall not pity." Just as here monetary payment (is being referred to), so, there, monetary payment.
R. Yehudah says: It is written here (19:21) "hand" and "foot," and elsewhere (Shemoth 21:24) "hand" and "foot." Just as "hand" and "foot" here refer to monetary payment, so, "hand" and "foot" there.
R. Yossi Haglili says: Whence is it derived that one should not go out to war unless he has hands, feet, eyes, and teeth? From (the juxtaposition of (19:21) "Your eyes shall not pity; a soul for a soul, an eye for an eye, a tooth for a tooth, a hand for a hand, a foot for a foot" with (20:1) "when you go out to war against your foes."