Here "your eye" refers to the whole person. AT: "you msut not look at him with pity" or "you must not show him mercy" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
This means that he was to throw the first stone at the guilty person. The word "hand" represents the whole person. AT: "you must be the first to strike him to kill him" (See: [[rc://en/ta/man/translate/figs-synecdoche]])