What is "petavatthu"

The Petavatthu is a Theravada Buddhist scripture, included in the Khuddaka Nikaya of the Pali Canon's Sutta Pitaka. It is composed of 51 verse narratives describing specifically how the effects of bad acts can lead to rebirth into the unhappy world of petas (ghosts) in the doctrine of karma. It gives prominence to the doctrine that giving alms to monks may benefit the ghosts of one's relatives (see Ancestor worship).