Ramayana. Vishnu is born as Rama and his Brothers.
Now at this time all the deities were there assembled to receive their share of the offerings made, and being assembled together they approached Brahma with a petition. "A certain wicked rakshasa named Ravana greatly oppresses us," they said, "whom we suffer patiently because thou hast granted him a boon -- not to be slain by gandharvas, or yakshas, or rakshasas, or gods. But now his tyranny becometh past endurance, and, O Lord, thou shouldst devise some method to destroy him." To them Brahama replied: "That evil rakshasa disdained to ask from me immunity from the attack of men: by man only he may and shall be slain." Thereat the deities rejoiced. At that moment there arrived the great God Vishnu, clad in yellow robes, bearing mace and discus and conch, and riding upon Garuda. Him the deities reverenced, and prayed him to take birth as the four sons of Dasharatha for the destruction of the wily and irrepressible Ravana. Then that one of lotus-eyes, making of himself four beings, chose Dasharatha for his father and disapeared. In a strange form, like a flaming tiger, he reappeared in Dasharatha's sacrificial fire and, greeting him, named himself as the messenger of God. "Do thou, O tiger amongst men," said he, "accept this divine rice and milk, and share it amongst thy wives." Then Dasharatha, overjoyed, carried the divine food and gave a portion of it to Kaushalaya, and another portion to Sumitra, and another to Kaikeyi, and then the fourth portion to Sumitra again. In due time four sons were born of them, sharing the self of Vishnu -- from Kaushalya, Rama; from Kaikeyi, Bharata; and from Sumitra, Lakshmana and Sastrughna; and these names were given them by Vashishtha.
Meanwhile the gods created mighty monkey-hosts, brave and wise and swift, shape-shifters, hardly to be slain, to be the helpers of the heroic Vishnu in the battle with the rakshasas.
The fours sons of Dasharatha grew up to early manhood, excelling all in bravery and virtue. Rama especially became the idol of the people and the favourite of his father. Learned in the Vedas, he was no less expert in the science of elephants and horses and in riding cars, and a very mirror of courtesy. Lakshmana devoted himself to Rama's service, so that the two were always together. Like a faithful shadow Lakshman followed Rama, sharing with him everything that was his own, and guarding him when he went abroad to exercise or hunt. In the same way Satrughna attached himself to Bharata. So it was till Rama reached the age of sixteen.
Now there was a certain great rishi named Vishvamitra, originally a Kshatriya, who by the practice of unheard-of austerities had won from the gods the status of brahma-rishi. He dwelt in the Shaiva hermitage called Siddhashrama, and came thence to ask a boon from Dasharatha. Two rakshasas, Maricha and Suvahu, supported by the wicked Ravana, continually disturbed his sacrifices and polluted his sacred fire; none but Rama could overcome these devils. Dasharatha welcomed Vishvamitra gladly, and promised him any gift that he desired; but when he learnt that his dear son Rama was required for so terrible and dangerous a service, he was cast down, and it seemed as though the light of his life went out. Yet he could not break his word, and it came to pass that Rama and Lakshman went away with Vishvamitra for the ten days of his sacrificial rites. But though it was for so short a time, this was the beginning of their manhood and of love and strife.
Vashishtha cheered Dasharatha's heart, assuring him of certain victory for Rama. So, with his father's blessing, Rama set out with Vishvamitra and his brother Lakshman. A cool breeze, delighted at the sight of Rama, fanned their faces, and flowers rained down upon them from the sky. Vishvamitra led the way; the two brothers, carrying their bows and swords, wearing splendid jewels and gloves of lizard-skin upon their fingers, followed Vishvamitra like glorious flames, making him bright with the reflection of their own radiance.
Arrived at the hermitage, Vishvamitra and the other priests began their sacrifice; and when the rakshasas, like rain-clouds obscuring the sky, rushed forward in horrid shapes, Rama wounded and put to flight Maricha and Suvahu, and slew the others of those evil night-rangers. After the days of sacrifice and ritual at Siddhashrama were over, Rama asked Vishvamitra what other work he required of him.