Narad Muni was the son of Lord Brahma. His devotion for Lord Vishnu is well known among the Hindus, through our scriptures and other old Hindu texts. While Lord Brahma is believed to be the real author of the Vedas, it is Narad Muni who conveys the message of the Vedas to the world.
Narad Muni was a wandering sage, and it is said that saints should stay away from the feelings of hatred, enmity, greed, pride etc. which are believed to take a man to doom. However, many stories prevail in our scriptures which show the sages being a victim of these feelings and then ultimately realizing their mistake only when the God intervenes.
There is an incident which talks about Narad Muni, one of the greatest sages falling a prey to pride. Narad Muni used to wander around the world singing praises of Lord Vishnu, through his self composed songs and the occasional "Narayan, Narayan". On the way, he saw a poor man who seemed upset and tensed and was in need of help. Narad Muni reached near him and inquired what the cause of the man's worry was.
As the man told, he was a rich trader but all his wealth was of no use as he had no child to make use of it. He requested Narad Muni to bless him with a boy child. While he said this, his eyes were filled with hope and pain. To this, Narad Muni said that it was Lord Vishnu where Narad Muni himself got all his blessings from. Hence, he affirmed that he would ask Lord Vishnu to grant him the wish of becoming a father.
With the man's message in his mind, Narad Muni went to Lord Vishnu. Lord Vishnu, in his abode Baikunth, was sitting in meditation. As he heard "Narayan Narayan", he understood it could be none other than Narad Muni. "Dear Lord, a devotee needs you", said Narad Muni. As Lord Vishnu heard this, he opened his eyes and asked who needed him and why.
The sage narrated the event of the rich merchant, and asked Lord to give him his blessings, so that he could become a father. To this, Lord Vishnu said that being a father was never written there in his destiny, and that he would not change a person's destiny as it causes a disturbance in the plans and the setup that nature has planned. Hence, nodding to what Lord Vishnu said and respecting his decision thus, Narad Muni left from there.
Years passed and Narad Muni once remembered about this rich merchant and thought to go and see him once. He headed over to the merchant's house. However, Narad Muni was surprised to see that the merchant was sitting with his four sons.
He rushed to the merchant and asked him who those four boys were. The merchant happily replied "thanks to you Oh Lord, it is all because of your blessings that I got blessed and have four sons today". A confused Narad Muni left the place, heading towards the abode of Lord Vishnu.
"Narayan, Narayan, dear Lord, how and when did you change the destiny of the merchant?" Lord Vishnu smiled and said - "there comes a time when I test the devotion of my devotees. Once, a divine sage came to Baikunth to see me, I was then crying with pain in my stomach. Seeing me thus, the sage asked how he could help me. I told him that the only way, this pain could be relieved was if I could get the blood of the heart of a human on earth."
Lord Vishnu continued, ''since, the sage was no more a human being and had become divine, his blood would be of no use. However, he started roaming around the world, in search of a human's blood. He told everybody that God needed their blood. But people would not trust him for this. Then he reached to the same merchant that you had told me about. The merchant not just recognised that he was a divine sage, but also trusted him. He even pierced his chest with a knife and gave him four drops of blood.
Pleased with his love and knowledge of the divine and the ordinary, and the dedication of the sage who wandered around the world to help me get relieved from the pain, I blessed the merchant.''