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: Nazir 53b — “Or a grave” — this is a sealed grave, for the Master said: impurity breaks through and ascends, breaks through and descends.
English: “Or a grave” — this is a sealed grave, for the Master said: impurity breaks through and ascends, breaks through and descends.
Identification of the grave that conveys impurity by vertical breakthrough.
A sealed grave conveys impurity that breaks through upward and downward.