Srimad Bhagvata Mahapurana: Book 10: Chapter 12: Verses 24-32
(If it is really the mouth of a serpent,) will it gulp us down when we have found our way into it ? If so, it will perish like the heron in a moment at the hands of Sri Krsna." Saying so and staring at the bewitching face of Sri Krsna (the Slayer of Baka), they went on, loudly laughing and clapping their hands. Hearing thus the talk-which was far from the truth--of those children, who were ignorant of the real fact, and thinking that the serpent, though real, appeared fictitious to them, and perceiving the python to be an ogre, the Lord, installed in the heart of all living beings, made up His mind to restrain His companions. Meanwhile the children along with the calves made their way into the bowels of the demon, but they were not (immediately) devoured by the ogre, who awaited the entry of Sri Krsna (the Slayer of Baka), remembering (as he did) the death of his relations (his brother Baka and sister Baki), that had been slain by Him. Perceiving the children-who, intact, accounted Him their sole Protector-as having slipped out of His control and having turned into fodder for the gastric fire of Agha (who was terrible as Death) and as (thus) reduced to a miserable plight, Sri Krsna, who vouchsafes protection to all, was moved with pity and at the same time astonished at the work of destiny.