As the Bhagavata tells it
Bhagavata Purana 10.56 to 57 · 2 min read
Satrajit of the Yadavas was a devotee of the Sun, and the Sun, pleased with him, gave him a jewel to wear. It was called Syamantaka. When Satrajit walked into Dvaraka with it at his throat, he shone so brightly that the people ran to Krishna. "The Sun himself has come to see you," they said. Krishna laughed. "That is only Satrajit, wearing his jewel."
The jewel gave its keeper eight measures of gold every day, and wherever it was kept there was no famine, no sickness and no snakebite. Krishna once asked Satrajit to give it to the old king Ugrasena, for the good of the whole city. Satrajit would not part with it.
One day Satrajit's brother Prasena put the jewel on and rode into the forest to hunt. A lion killed him and his horse and took the jewel away in its mouth. In a cave in the hills, Jambavan, the king of the bears, killed the lion and gave the bright stone to his little son to play with.
Prasena did not come home. Satrajit sat in his house and said aloud what half the city was thinking. "Krishna asked me for the jewel and I said no. Now my brother has gone into the forest wearing it, and he is dead."
The talk reached Krishna, and it stung. He took some of the citizens with him and followed Prasena's trail. They found the horse and the man, dead, and beyond them the lion, also dead, and beyond the lion the tracks of a bear going up into the hills. The tracks ended at a cave.
Krishna told the others to wait and went in alone. Deep in the dark he found the child playing with the jewel. The nurse screamed, and Jambavan came.
They fought with stones and trees and then with bare fists, for twenty-eight days. Outside, after twelve days, the citizens gave Krishna up for dead and went home. In the cave, the old bear began to tire, and then to wonder. "I know only one being who could stand against me," he said at last. "The one I served long ago, when he was Rama. You are he." He bowed down, gave Krishna the jewel, and gave him his daughter Jambavati as well.
Krishna walked back into Dvaraka with a bride and the jewel. He called Satrajit to the assembly, told the whole story in front of everyone, and handed the jewel back.
Satrajit hung his head. He had shamed a blameless man before the city. To make amends he gave Krishna his daughter Satyabhama in marriage, and the jewel with her. Krishna took the daughter. "Keep the jewel," he said. "Only let us share the gold."
As it is told on Ganesh Chaturthi
Maharashtra and North India · with the Ganesha vrata · 1 min read
On Ganesh Chaturthi the moon is not to be looked at, because the moon once laughed at Ganesha and was cursed for it. Whoever sees that night's moon, the curse goes, will be falsely accused of a theft.
The tellers say that even Krishna was caught. On the Chaturthi of Bhadrapada, as he was milking a cow, he saw the moon reflected in the pail. Soon after, Prasena went into the forest wearing the jewel, and Krishna was blamed.
He went to the forest and the cave and brought the jewel back, and still the talk did not stop. Then Narada came to him. "You saw the moon on the fourth day of the bright half of Bhadrapada," he said. "That is why the blame sticks to you. Keep the Ganesha vow, and it will leave you."
Krishna kept the vow, and his name was cleared. Ganesha then made a promise. Anyone who caught sight of the Chaturthi moon by mistake, and afterwards listened to the story of the Syamantaka jewel, or told it, would be free of the false blame.
So families who see the moon that night sit down and tell this story, and the priests recite a single verse that tells it in brief. "The lion killed Prasena. Jambavan killed the lion. Do not cry, little one. This Syamantaka is yours." It is the nurse's lullaby from the cave, and it is said to be enough.