Mahabharata 1.3.75

1.3.75

tamaśvināvāhatuḥ |
prītau svastavānayā guruvṛttyā |
upādhyāyasya te kārṣṇāyasā dantāḥ |
bhavato hiraṇmayā bhaviṣyanti |
cakṣuṣmāṃśca bhaviṣyasi |
śreyaścāvāpsyasīti || 75 ||

The twin Aswins, thus invoked, appeared and said, 'We are satisfied. Here is a cake for thee. Take and eat it.' And Upamanyu thus addressed, replied, 'Your words, O Aswins, have never proved untrue. But without first offering this cake to my preceptor I dare not take it.' And the Aswins thereupon told him, 'Formerly, thy preceptor had invoked us. We thereupon gave him a cake like this; and he took it without offering it to his master. Do thou do that which thy preceptor did.' Thus addressed, Upamanyu again said unto them, 'O Aswins, I crave your pardon. Without offering it to my preceptor I dare not apply this cake.' The Aswins then said, 'O, we are pleased with this devotion of thine to thy preceptor. Thy master's teeth are of black iron. Thine shall be of gold. Thou shall be restored to sight and shall have good fortune.'