佛說觀佛三昧海經 7.28

7.28

Then the Bhagavat withdrew his supernormal footstep and came out of the rock cave. Together with the monks, he visited the places of his past lives when he was a bodhisattva: the place where he gave away his two children, the place where he cast his body to the hungry tigress, the place where he gave away his head, the place where his body was gouged for a thousand lamps, the place where he plucked out his eyes in giving, and the place where he cut his flesh to ransom the dove. To all such places the dragons followed. At that time, when the dragon king heard that the Buddha was returning to his country, he wept with streaming tears and said, 'Bhagavat! I pray that the Buddha abide here always; how can you abandon me? If I do not see the Buddha, I will commit evil deeds and fall into the wretched destinies.'
Then the Bhagavat comforted the dragon king: 'I have accepted your invitation to sit in your cave for one thousand five hundred years.'
Then the young dragons pressed their palms together with fingers interlaced, entreating the Bhagavat to return into the cave. When the dragons saw the Buddha seated in the cave, water issued from the upper part of his body and fire issued from the lower part of his body, performing the eighteen transformations. When the young dragons saw this, their resolute aspiration for the Path increased even further. Śākyamuni Buddha leaped into the rock, like an image of a person's face seen in a bright mirror; all the dragons saw the Buddha within the rock, shining forth outside. Then the dragons joined their palms in joy; not leaving their pool, they constantly beheld the Buddha-sun.