Commento su Esodo 21:25

כויה תחת כויה BURNING FOR BURNING — כויה is a burn produced by fire. Up to here (i .e. v. 24) Scripture has spoken of a bodily injury that is attended by a decrease of the market-value of the person injured; here, however, it speaks of a case in which there is no decrease of value but pain alone: if, for instance, a man burns another on his nails with a hot spit, we estimate how much a person like him (the injured) would be willing to accept for undergoing a pain like this, and such an amount the other has to pay as indemnity (Bava Kamma 84b).

כויה תחת כויה; even though the examples mentioned here do not involve loss of an entire organ or limb, the principles applying to compensating the victim are based on the same considerations

(Exodus 21:25) "A burn for a burn": If you say (the meaning is that he burned him and spilled his blood, this is already subsumed in "a wound for a wound." If you say that he made a welt, this is already subsumed in "a welt for a welt." How, then, is "a burn for a burn" to be understood? As his burning him on his nail or on the sole of his foot without leaving an impression, lading him with stones and causing him suffering thereby, placing snow on his head and making him cold — in which instances he compensates him for his suffering. But if he were frail, indulged, and pampered, how much more so is his "suffering" allotment to be doubled. This is the (type of) suffering intended in "a burn for a burn."