Numbers 19:16

And whosoever toucheth one that is slain with a sword in the
open fields
That is killed by another, that dies a violent death, either by the sword or other means; one that touched such an one was unclean, or that touched the sword with which he was slain, as the Targum of Jonathan adds: "or a dead body": that dies a natural death, or suddenly, or in any way:

or a bone off a man;
dug out of a grave, and lying by itself:

or a grave;
the Targum adds, either the covering or side of a grave:

shall be unclean seven days;
all which has respect to the defiling nature of sin, which is the cause of death and the grave.