The Buddha of the Great Canon expounds The Mahayana Sutra on Repaying Kindness
Thus have I heard: Once the Buddha was on Vulture Peak, surrounded by the Great Assembly. At that time, Ananda entered the city to beg for food. In the city there was a man who tended filially to his parents; their property having been lost to them, he carried his parents on his shoulders as he went about begging. All the good food he offered to his parents while he himself ate that which was disgusting. Ananda praised the man for supporting his parents, (at that) time such a person being extremely difficult (to find).
There happened by six masters and disciples, holders of heretical ideas, who had savagely burned the True Law, and whose hearts harbored envy. To Ananda they said, “Your master of the Shakya clan proclaims himself to be a person of excellence, endowed with great merit. But his is a hollow name with no basis in actual practice. He has set aside his parents to leave the city, not knowing the kindness he has (personally) received from them. This is not a filial person.”
When Ananda heard this, in his heart he felt ashamed. Returning to the Buddha he asked, “Within the Buddha’s Law, why] isn’t there a bias toward filial support for parents?” The Buddha replied, “Who instructed you to ask this?” Ananda said, “While begging for food, I came upon six masters and disciples, and saw them slandering by such as I have stated above.” The World-Honored One let out a little smile, emitting a five-colored light that reached all of the Buddhas of the Ten Directions. The bodhisattvas of those lands together intoned, “What causes this radiance?” The Buddhas of those lands replied, “In the Saha realm, there is a Buddha named Shakyamuni who to the multitude is expounding The Mahayana Sutra for Repaying Kindness desiring to cause all creatures to be filial and caring toward their fathers and mothers; as such he releases this radiance.”
At that time, upon the Buddha’s body appeared the five forms of reincarnation and one-by-one within these forms appeared limitless small worlds, so numerous that their forms and characteristics were beyond thought or description, one body corresponding to (each of) the myriad beings with enough so that all receives a body. It is because of the receiving of a body that all the myriad creatures were once the parents of the Buddha, and moreover, that the Buddha once was the parent of every sentient being. Therefore, he (Shakyamuni as a bodhisattva) constantly cultivated difficult practices, undertaking painful austerities so difficult to practice that he was able to renounce what is difficult to renounce. Diligently keeping up his perseverance, he perfected the 10,000 practices, never resting, never growing weary at heart. It is because of one’s (efforts) to teach and nurture one’s father and mother that one is able to quickly become a celestial Bodhisattva. (All this) is due to the virtue of being filial.