Lord Krishna was consumed with the desire to have a son. So he went to seek the advice of a particular sage. When the sage saw Lord Krishna, he was overwhelmed with joy. Everybody was shouting, “Krishna has come, Krishna has come!” and they all started worshipping Krishna.
The sage asked Krishna, “Please tell me what I can do for you. Is there anything that you would like me to do?”
Krishna answered, “It is a very simple thing that I want. I want to have a son. Please tell me how I can have a son.”
“Only Lord Shiva can help in this matter,” said the sage. “You have to pray to Lord Shiva. First, you must gather one thousand flowers. With these flowers you must worship Lord Shiva for many years. When Lord Shiva is pleased with your worship, you will be granted a son.”
Krishna left the cottage of the sage and entered into seclusion. He put ashes all over his body and clothed himself in the bark of a tree. For years and years he prayed, only to have a glimpse of Lord Shiva and to ask him for a boon.
With her third eye, Parvati saw that Krishna was praying and praying all alone in the heart
of the forest. She said to her husband, “My Lord, what are you doing? Why are you not responding? Lord Krishna has been worshipping you, only you, for so many years.”
“What do you want me to do?” asked Shiva.
“Just go and stand before him,” pleaded Parvati. “As a matter of fact, let us go together.”
Both Parvati and Shiva appeared before Krishna. Shiva said to him, “What are you doing? Why should you, of all people, pray to me? You are Narayana, you are Vishnu, you are the avatar of this era, you pervade everything. Why then are you praying to me?”
Krishna responded, “Lord Shiva, I know that you are the only one who can fulfill my desire.”
“Is there any desire which you yourself cannot fulfill?” asked Shiva.
“I was told that only you can fulfill this particular desire. Therefore, I have come to you,” answered Krishna.
“What is your desire?” asked Shiva.
“I wish to have a son exactly like you,” Krishna said to Shiva. “It has to be exactly like you, otherwise I do not want it.”
Shiva and Parvati both smiled and immediately Shiva granted Krishna the boon. Krishna returned home and, after some time, his wife, Jambavati, bore a son. They named him Samba.
What does it mean to have a son exactly like Shiva? On the one hand, Shiva is always lost in trance. But, on the other hand, Shiva's function is to destroy. From destruction comes transformation. This boy, Samba, did many unbearable things during his life. Eventually he brought about the total destruction of Krishna's family. So you can say that Krishna knew that transformation was needed and transformation must be preceded by destruction. That is why he prayed to have a son like Shiva.
from The Earth-Illumination-Trumpets of Divinity's Home (Stories from the Indian Scriptures: the Puranas)
by Sri Chinmoy