en_tn_condensed/deu/13/09.md

your hand will be the first on him to put him to death

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)

the hand of all the people

Here "hand" represents the whole person. AT: "the other people will join you" (See: rc://en/ta/man/translate/figs-synecdoche)