Here "eyes" refer to the whole person. Alternate translation: "You must not pity him" or "You must not show him mercy" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
Here the phrases are shortened because the meaning is understood. It means the people must punish a person in the same way that he harmed another person. (See: [[rc://en/ta/man/translate/figs-ellipsis]])