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.

The scripture also includes stories of Maudgalyayana's travels to the Hungry Ghost realm and his discussions with Hungry ghosts and his understanding of the realm. It also includes a story of how Sariputta rescued his mother from hell by making offerings to the monks as a form of merit-making to increase the chance of a hungry ghost being reborn as a higher being. A version of this legend is also told in the Mahayana Ullambana Sutra, where Sariputta is replaced by Maudgalyayana, which also discusses the realm of the Hungry ghosts.

The scripture gave prominence to the doctrine that giving alms to monks may benefit the ghosts of one's relatives seen in the Hungry Ghost Festival and ceremonies conducted in Cambodia, Sri Lanka, Thailand and Laos.

...
Wikipedia