In Shakespeare's day it was customary to move bones from the graveyard, and the tombs within the church, into a charnel house to make way for more burials. From time to time, the bones in the charnel house were burned. This was commonly known as the bonefire (thus bonfire) of the vanities.
Shakespeare was having none of that! He had the following curse inscribed on his grave:
GOOD FRIEND FOR JESUS SAKE FORBEARE,
TO DIGG THE DUST ENCLOASED HEARE.
BLESE BE THE MAN THAT SPARES THES STONES,
AND CURST BE HE THAT MOVES MY BONES.
A rubbing of the inscription is displayed on the tombstone.