Well it is said that Shri Narsingh was another form of Lord Vishnu who was Half Lion and Half Human. It is said that, Hiranyakashipu, a demon king used to ill treat his son Prahalad because he used to worship lord Vishnu. Also Hiranyakashipu was having boon from the Lord Brahma that he cannot be killed by man, animal, day or night, in the sky or on earth, inside or outside, not by any astra or shastra, not in any of the 12 months. And his cruel practices upon on his son increased to several folds. Once he tried to kill his son with the help help of his sister Holika. Hiranyakashyapa took the help of her sister named as ‘Holika’. She was also as cruel and dreadful as his brother. Both of them made plans in which Holika was to sit on fire with Prahalad on her lap. As ‘Holika’ was blessed with drape, by which she cannot be burnt by fire or Agni. But at the time of sitting on fire with Prahalad on her lap, a strong wind blown in and it carried drape away from the Holika body and came on the Prahalad body. Thus Prahalad got saved and Holika got burnt.
So one day in the evening, from the pillar of the Palace in which Harinyakashipu used to live, Lord Narsingh came out. Lord Narasimha told Hiranyakashyapa that how he is making misuse of the boon given to him by the Lord Brahma. He also reminded of that, how he has started considering himself above all and his self attitude is increasing day by day. And then Lord Narsingh moves towards Hiranyakashyapa and took him on the step of the Palace and tore apart his stomach. Since it was evening, so it was neither day nor night. It was Adhik Maas, so no under the 12 month too. Since Lord Narashimha tore apart his stomach, so no astra or shastra were used. So this marks the win of the good over the evil.
And from this day only Shri Narsingh Jayanti is being celebrated. Lord Narashimha has always been related with protector of human being. Whosoever is in any type of difficulty, it is said that Narashimha will help his devotees. This whole event shows how Lord Vishnu used to do different types of Leela to help and safeguard the interest devotes of him.
How people celebrate Shri Narasimha Jayanti
Country wide this festival cum Jayanti is being celebrated with great devotion, reverence and joy. People wake up early in the morning and take bath accompanied by new cloths. Then they go to temple for worshiping lord Vishnu. At several places, people keep fast and they spend most of the time while worshipping lord Vishnu.
At various like temple vicinity or the Kirtan Ghar, large events are organized in which chanting of shlokas, stories related to Lord Vishnu is carried out. At various Ramayana katha is also preached among the crowd.
People decorate the idol of Lord Vishnu with new cloths and do the Abhishek. A very famous village named as Tadavas is having a big temple of Lord Narashimha, and there crowd in large numbers gather to offer their prayers.
In various places, play is organized that depicts the life of Lord Vishnu like Ramayan etc. The attendance of crowd in such type of events is immense and people enjoy much this type of events. Prasad (Holy offering from god) is made and distributed among the crowd at the end of the prayers.