And whoever in the open field touches one who is slain with a sword, or a dead body, or a bone of a man, or a grave, shall be unclean seven days.
Torah Temimah: Sifrei — “Or a bone of a man” — this is a limb from a living person; just as a man has flesh, sinews and bones, so a limb from a living person [must have] flesh, sinews and bones as in its natural state.
English: “Or a bone of a man” — this is a limb from a living person; just as a man has flesh, sinews and bones, so a limb from a living person [must have] flesh, sinews and bones as in its natural state.
Requirement of complete natural composition for a limb from a living person.
A limb severed from a living person conveys impurity only when it contains flesh, sinews and bone in their natural configuration.