Vidhura's curse in his previous birth as Yama

Mandavya rishi, a pious and famous Rishi or sage built a hut and was living and meditating in a jungle and doing his service to God. One day some thieves entered the palace of the King and stole valuables from there and ran away. After stealing everything they were going to the forest and on the way saw a sage doing penance, meditating  under a tree. One of the thieves threw an expensive gold chain on the neck of the sage and they went away. The palace soldiers came after them. The thieves  threw the  necklace on the meditating sage, which fell on his neck  thinking that the soldiers would stop pursuing them. 

The soldiers came to the tree where the sage was meditating, saw the necklace on his neck. The sage was concentrating on his penance and was not aware of what happened to him. They went back to the king and informed him about this sage with the chain on his neck. The King in a fit of rage asked the soldiers to catch the sage and impale him on a sharp knife in sitting position.  This is a punishment in olden days  and impalement was carried out on a long erect knife fixed no  a  dais and on which the accused would be asked to sit cross legged. The knife would slowly pierce him from his bottom and come out through his head. In olden days it was a punishment, a serious punishment for adultery, stealing, murder etc.

The soldiers took the sage to the street corner and impaled him in sitting position. The knife went from his bottom and came out through his head. But he did not die but was still meditating, but with excruciating pain. When evening came, the other sages, his friends,  came to enquire after him in the guise  of birds as he did not return to his abode. They found him impaled in the knife and asked him why he was punished like this. The sage replied that these were the fate of his sins of previous birth. The soldiers guarding him found birds talking to him and he was still alive. They were frightened and sensed something was wrong and  went and informed the king about this.

The king understood that some thing wrong had been committed against the sage. He came running and asked the soldiers to pull out the sage from the knife and fell on his feet and apologized for his mistake. The sage just ignored him and went to the god of Justice Yama and asked him why he had to undergo this punishment when he had not done any mistakes in his whole life.  

Yama who had the records of everybody's goods and sins  told him that as a young boy the sage was catching and maiming butterflies and for that reason he had to undergo this punishment.

The sage got wild. He said "Yama, you do not know the justice. A boy under twelve years does things because of his ignorance and these could not be construed as sins, so you have committed the injustice and I had to undergo the punishment. Anybody  committing any sins below the age of twelve could not be considered as sin. Hence I curse you to be born as Vidhura and with all your knowledge and intelligence nobody would listen to your advices and ignore and insult you. You will suffer like this till your death."

Thus the God of justice was born as Vidhura, the brother of Yudhishtra & Pandu but through a servant maid by Rishi Vyasar. He was always insulted by Duryodhana.