Story of Shani Dev and Surya Dev
As per the story in our ancient religious books, Lord Sun entrusted each of his sons the work of one world. However, Shanidev was not satisfied with it and he started planning to attack the other worlds in order to take them under his territory. Lord Sun couldn't’t bear with such an action of Shanidev and tried his best to bring him round.
However when Shanidev didn't’t listen to him, he went to Lord Shiva and asked him to forbid Shanidev doing this mischievous act. Now, Shanidev did not comply with it and got ready to fight against his deity, Lord Shiva. He scarred Shiva Sena inclusive of Veerbhadra and Nandi etc. At this, Lord Shiva opened his third eye (the eye of destruction) and the slayer aspect of Shanidev in response. With the intersection of both the sights, a new and a rare auspicious bright light was created, which covered the whole world of Shanidev.
Looking at this, Shiva, the Lord of destruction attacked over Shanidev by his trident and by this attack Shanidev became unconscious. Now, Sun got restless because of the love for his son and prayed humbly to Lord Shiva to save his life.Lord Shiva was moved away at the request of Lord Sun and saved the life of Shanidev.
When Shanidev gained consciousness, he apologised from Lord Shiva and acceded to his all powerfulness and finally submitted himself to Lord Shiva, who accepted him at his service. Lord Shiva, since that day entrusted him with the responsibility of making living beings to undergo the results of their misdeeds.
Since that day, Shanidev started performing his duty. He is never partial in giving them the results of their misdeeds. He is neither a friend nor a foe to anyone. He does his duty to all; the gods or the devil gods; to an ascetic or a chaste; to a sage or a household, he treats them all equally. He (Shanidev) does not spare anyone in punishing for his misdeeds.