Narasimha Chaturdashi is the divine appearance day of Lord Narasimhadev. Lord Krishna came in the incarnation of half man, half lion, just to protect His dearmost devotee Bhakta Prahlad from the demon Hiranyakashipu.
Hiranyakashipu, the father of Prahlad Maharaj, was an extremely powerful demon controlling the three worlds. He was very proud of his abilities and aroused fear in everyone including the demigods. He devised innumerable plans to kill his own son Prahlad. The Lord will tolerate any hatred towards Himself, but He will never tolerate anything that will put His devotee in danger.
And thus, to save His most dear devotee Prahlad, He burst forth from the pillar and came to kill Hiranyakashipu. Prahlad was protected because of his unflinching faith in the Supreme Lord.
On this most auspicious day, we can offer at the Lotus Feet of Lord Narasimhadeva this beautiful prayer by Bhakti Vinoda Thakura:
e dusta hrdaye kama adi ripu chaya
kutinati pratisthasa sathya sada raya
hrdaya-sodhana ara krsnera vasana
nrsimha-carane mora ei to’ kamana
“Within my sinful heart the six enemies headed by lust perpetually reside, as well as duplicity, the desire for fame, plus sheer cunning. At the lotus feet of Lord Narasimha, I hope that He will mercifully purify my heart and give me the desire to serve Lord Krsna”.