Story
Krishna’s Tapasya for a child
Krishna was not having a child for many years. So, desirous of obtaining a son, Krishna went to visit the sage Upamanyu at his forest hermitage. The constant chanting of the Vedas could be heard always from the hermitage where Sages came from all over the country to come and do sadana. The sacred river Ganga flowed past the hermitage and even wild animals lose their ferocity on the sight of revered sages.
Krishna greeted the sages and they worshipped him in return. Sage Upamanyu welcomed Krishna and said, “Our meditation has been amply rewarded by your visit. It looks to me that the great Vishnu has himself come to grace us by your presence. But is there any particular reason as to why you have come to the hermitage?”
“I wish to meet Shiva,” replied Krishna. “How does one get to met him?”
“Shiva appears if a devotee performs difficult tapasya,” said Upamanyu. ”It helps if the meditation is accompanied by great faith.”
Krishna went into seclusion, put ashes all over his body, clothed in tree bark and prayed for a glimpse of Shiva. After some years both Parvati and Shiva appeared before Krishna and asked his desire.
Krishna said, "I want a son of your character". Shiva granted Krishna the boon. After some time Krishna's wife Jambavati gave a birth to a baby, they named him Samba.
As Shiva's main function is to destroy creation the son born with Sivas grace became a cause of the destruction of his entire race of Yadavas.