The Bodhisatta was once an ascetic who had many followers studying with him in the Himalayas. One of his students kept a pet viper in a bamboo tube. The Bodhisatta told him vipers cannot be trusted and he should let it go—if he didn’t, the snake would kill him. But the man told the Bodhisatta he loved the snake as if it were his own child and did not follow the advice.
A short time later all the ascetics went out into the forest to gather fruit for a few days. Upon their return, the student opened the bamboo tube to feed his snake, as he had always done before, but this time the snake was angry at being kept in the cage for so long and it bit his hand, killing him instantly.
In the Lifetime of the Buddha
One of the Buddha’s disciples, who had been the ascetic who kept the viper as a pet in an earlier birth, was stubborn and the Buddha told him this story as a warning that stubbornness can have bad results.