Vishnu is born as Rāma & his Brothers
The four sons of Dasharatha grew up to early manhood, excelling all in bravery and virtue. Rāma especially be came 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 Rāma's service, so that the two were always together. Like a faithful shadow Lakshman followed Rāma, 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 Rāma reached the age of sixteen.
Now there was a certain great rishi named Vishvāmitra, originally a Kshatriya, who by the practice of unheard-of austerities had won from the gods the status of brahmā-rishi. He dwelt in the Shaiva hermitage called Siddhāshrāma, and came thence to ask a boon from Dasharatha. Two rākshasas, Mārīcha and Suvāhu, supported by the wicked Rāvana, continually disturbed his sacrifices and polluted his sacred fire; none but Rāma could overcome these devils. Dasharatha welcomed Vishvāmitra gladly, and promised him any gift that he desired; but when he learnt that his dear son Rāma 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 Rāma and Lakshman went away with Vishvāmitra 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.
Vāshishtha cheered Dasharatha's heart, assuring him of certain victory for Rāma. So, with his father's blessing, Rāma set out with Vishvāmitra and his brother Lakshman.
