Enlightenment
The Bhagavata Purana describes the story of Narada's spiritual enlightenment: He was the primary source of information among Gods, and is believed to be the first journalist on Earth. He never married but claimed to have 60 wives. In his previous birth Narada was a Gandharva (angelic being) who had been cursed to be born on an earthly planet due to some offense. He was born as the son of a maid-servant of some particularly saintly priests (Brahmins). The priests, being pleased with both his and his mother's service, blessed him by allowing him to eat some of their food (prasad), previously offered to their lord, Vishnu.
Gradually Narada received further blessings from these sages and heard them discussing many spiritual topics. After his mother died, he decided to roam the forest in search of enlightenment in understanding the 'Supreme Absolute Truth'.
Reaching a tranquil forest location, after quenching his thirst from a nearby stream, he sat under a tree in meditation (yoga), concentrating on the paramatma form of Vishnu within his heart as he had been taught by the priests he had served. After some time Narada experienced a vision wherein Narayan (Vishnu) appeared before him, smiling, and spoke "that despite having the blessing of seeing him at that very moment, Narada would not be able to see his (Vishnu's) divine form again until he died". Narayan further explained that the reason he had been given a chance to see his form was because his beauty and love would be a source of inspiration and would fuel his dormant desire to be with the lord again. After instructing Narada in this manner, Vishnu then disappeared from his sight. The boy awoke from his meditation both thrilled and disappointed.
For the rest of his life Narada focused on his devotion, meditation upon and worship to Vishnu. After his death Vishnu then blessed him with the spiritual form of "Narada" as he eventually became known. In many Hindu scriptures Narada is considered a saktyavesa-avatara or partial-manifestation (avatar) of God, empowered to perform miraculous tasks on Vishnu's behalf.
Actually Narada is not an saint, he is the incarnation of Lord Narayana, in 1st canto Srimad Bhagavat Mahapuran, it is mentioned Devarshi Narada is the 3rd incarnation of Lord Vishnu out of 22 incarnations. He incarnated to teach Bhakti yoga, he is also called Bhaktya Avatara. Narada played very significant role with Lord Vishnu almost in all Puranas including Ramayan and Mahabharat, Krsna says in Gita, out of all the devine sages I am Narada. Narada is the one who give Ramayan knowledge to sage Valmiki and he gave Bhagavat Mahapuran knowledge to Veda Vyas.
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