Numbers 19:11, 16, 18

‘The one who touches the corpse of any person shall be unclean for seven days.

Also, anyone who in the open field touches one who has been slain with a sword or who has died naturally, or a human bone or a grave, shall be unclean for seven days.

A clean person shall take hyssop and dip it in the water, and sprinkle it on the tent and on all the furnishings and on the persons who were there, and on the one who touched the bone or the one slain or the one dying naturally or the grave.