After he attained arhatship, he began to think deeply of his parents, and wondered what happened to them. He used his clairvoyance to see where they were reborn and found his father in the heavenly realms i.e the realm of the gods. However, his mother had been reborn in a lower realm, known as the Realm of Hungry Ghosts. His mother took on the form of a hungry ghost--- so called because it could not eat due to its highly thin & fragile throat in which no food could pass through, yet it was always hungry because it had a fat belly. His mother had been greedy with the money he left her. He had instructed her to kindly host any Buddhist monks that ever came her way, but instead she withheld her kindness and her money. It was for this reason she was reborn in the realm of hungry ghosts.

Mahāmaudgalyāyana eased his mother's suffering by receiving the instructions of feeding pretas from the Buddha. The Buddha instructed Mahāmaudgalyāyana to place pieces of food on a clean plate, reciting a mantra seven times, snap his fingers then tip the food on clean ground. By doing so, the preta's hunger was relieved and through these merits, his mother was reborn as a dog under the care of a noble family.

Mahāmaudgalyāyana also sought the Buddha's advice to help his mother gain a human birth. The Buddha established a day after the traditional summer retreat (the 15th day of the seventh month in the lunar calendar, usually mid-to-late August) on which Mahāmaudgalyāyana was to offer food and robes to 500 bhikkhus. Through the merits created, Mahāmaudgalyāyana's mother finally gained a human birth.

Due to Confucian influence, the offering became directed towards ancestors rather than the Sangha and ancestor worship has replaced the simple ritual of relieving the hunger of pretas. However, most Buddhist temples still continue the ancient practice of donating to the Sangha as well as to perform rituals for the hungry ghosts.