On a certain day, while the Buddha was in residence at the Pipphali Cave, he made his round of Rajagaha for alms and after he had returned from his round for alms and had eaten his breakfast, he sat down and using psychic powers surveyed with Supernormal Vision all living beings, both heedless and heedful, in the water, on the earth, in the mountains, and elsewhere, both coming into existence and passing out of existence.
The Buddha, seated at Jetavana, exercised supernormal vision and pondered within himself, “With what is my son Mahakassapa occupied today?” Straightaway he became aware of the following, “He is contemplating the rising and falling of living beings.” And he said, “Knowledge of the rising and falling of living beings cannot be fully understood by you.
Living beings pass from one existence to another and obtain a new conception in a mother’s womb without the knowledge of mother or father, and this knowledge cannot be fully understood. To know them is beyond your range, Mahakassapa, for your range is very slight. It comes within the range of the Buddhas alone, to know and to see in their totality, the rising and falling of living beings.” So saying, he sent forth a radiant image of himself, as it were, sitting down face to face with Mahakassapa.
Source: Dhammapada(Verse 28)
