"Suppose, bhikkhus, that a person was to throw a yoke with a single hole into the great ocean, and it was carried about in all directions by the winds. Suppose there were a blind tortoise that emerged from the ocean once every hundred years.

What do you think, bhikkhus, would that tortoise put his neck through the hole in the yoke? − He might, bhante, after some very long period of time. − Sooner, bhikkhus, would that blind turtle put his neck through the yoke than would a fool escape back to the human realm once having fallen to a lower realm (vinipāta).

Why is that? Because there is no dhamma-faring there, no peace, no doing of good deeds or making of merit. There is only mutual devouring there; there the strong consume the weak.

If, bhikkhus, that fool after some long time regains the human state it is into a low family that he is born; a family of outcastes, hunters, bamboo gatherers, carters or refuse cleaners. Among such clans is he reborn. There he is poor; he finds little food with much difficulty. There clothing is hard to come by. He is of bad colour, ugly, deformed, sickly, blind or crippled or palsied. He gets no food, drink, clothing, vehicles, garlands, dwelling, bedding or lights. There he misconducts himself by body, speech and mind and at the break-up of the body he arises after death in a lower birth, even in niraya. Such is the nature of the total and utter fool."

Bālapaṇḍita Sutta