Upamanyu is tested and rewarded by the Ashvins
Upamanyu is tasked with tending his preceptor's cows. Each time his teacher sees him healthy, he forbids the source of his sustenance — alms, milk, even the froth the calves leave behind. Starving, Upamanyu eats poisonous leaves, goes blind, and falls into a well.
Ayoda-Dhoumya had a disciple named Upamanyu. He told him, "Go, my son, and look after my cows." Upamanyu did. Each evening he returned, stood before his preceptor, and saluted him respectfully.
Noticing his disciple was fat and healthy, the preceptor asked how he supported himself. Upamanyu said, "I support myself by begging." The preceptor replied, "You should not use alms you receive from begging without first offering them to me." Upamanyu agreed.
The next evening, the preceptor saw he was still fat. "I take all your alms away from you. How do you support yourself now?" Upamanyu explained that after giving his alms to his teacher, he went out to beg a second time for himself. The preceptor said this was covetous and deprived others. Upamanyu agreed.
The pattern repeated. Upamanyu admitted he lived on the cows' milk. His preceptor forbade drinking milk without permission. Upamanyu agreed. Finally, he confessed to drinking the froth the calves threw out while suckling. His preceptor forbade that too, saying it deprived the calves. Upamanyu agreed.
Now forbidden from every source of food, Upamanyu tended the cattle without eating. One day in the forest, suffering from hunger, he ate the leaves of the arka tree. The leaves were acrid, pungent, bitter, and unripe. They affected his eyes, and he went blind. Wandering blindly, he fell into a well.
When he did not return, his preceptor told the other students, "I have forbidden Upamanyu everything and perhaps he is angry. That is why he has not returned." He went to the forest and called out loudly, "O Upamanyu! Where are you? Come here, my son."
Upamanyu replied from the well. The preceptor asked how he fell. Upamanyu explained about the arka leaves and his blindness. His preceptor told him, "Sing praises of the two Ashvins. Those divine physicians will restore your eyesight."
Upamanyu began to worship the Ashvins with hymns from the Rig Veda, praising them as the first-born beings, creators of the sun and the directions, the weavers of night and day.
Pleased, the Ashvins appeared. "We are pleased. Here is a cake. Take it and eat it."
Upamanyu replied, "O Ashvins! Your words can never be false. But I cannot eat this cake without offering it to my preceptor."
The Ashvins said, "Many years ago, your preceptor once worshipped us. We gave him a cake. He ate it without offering it to his preceptor. You should do what he had then done."
Upamanyu stood firm. "O Ashvins! I crave your pardon. I cannot eat this cake without offering it to my preceptor."
The Ashvins said, "We are pleased with your devotion to your preceptor. Your preceptor has teeth made of black iron. Yours will be golden. Your sight will be restored and you will have good fortune."
His sight returned. He went back to his preceptor, saluted him, and told him everything. His preceptor was very pleased and confirmed that Upamanyu would obtain good fortune as promised, and all the Vedas would be manifest to him. This was his trial.