Seven days later, Aniruddha and several other princes left the palace with a servant named Upali, the palace barber. When then reached a forest, they told Upali to shave their heads. They took off their clothes and donned monks' robes. They also gave the ornaments they were wearing to Upali, because they would not need these ornaments once they became monks, and because they wanted to show their appreciation for Upali's many years of service. When they arrived at the place where the Buddha was staying, the Buddha tols them to stay in a house for seven days to get rid of their self-identities as princes. After that, they could join the sangha.

When they came out of the house seven days later, they were officially accepted as monks. But to their surprise, they discovered that Upali was among the assembly, dressed up as a monk. "upali came to me and asked me to accept him," the Buddha explained. "I agreed to his request. Since he joined the assembly before you did, he is senior member, so you should prostrate yourselves before him to show your respect. Remember, becoming a monk means you do not have any trace of egoism." And so they prostrated themselves most sincerely before Upali.

One day, Aniruddha fell asleep during one of the Buddha's lectures, and the Buddha admonished him for missing a chance to hear one of his precious sermons. Aniruddha felt so embarrassed that he vowed before the Buddha never to sleep again as long as he lived. Because he refused to sleep at any time, he slowly developed an eye ailment. The Buddha heard about this, and he went to see Aniruddha. "During your spiritual cultivation, you must still eat to sustain life, and sleep is food for your eyes. All creatures need food to stay alive, and we need sleep to stay healthy, so you must sleep to protect your eyes."

"Buddha,"Aniruddha replied, "I have vowed never to sleep again and I shall observe that vow." Several days later, he lost his eyesight completely.